feat(files): @shade/files 0.3.0 — E2EE filesystem RPC primitive

M-Files-1..6 land the full files-RPC layer + everything 0.3.0 needs to
ship. Apps keep their own UI; this layer ships the typed RPC, the
streams bridge for content I/O, and production hooks (rate limit,
retention, fingerprint gate, metrics).

@shade/files (NEW)
- Standard ops: list/stat/mkdir/delete/move/read/write/getThumbnail with
  Zod-validated wire schemas + clean user-handler types.
- Custom ops: typed via TypeScript declaration merging on CustomOpsMap
  + per-op Zod schemas; client.custom('app.foo', {...}) is fully typed.
- Content I/O: inline (≤ 256 KiB plaintext) base64-in-RPC; streams
  (> 256 KiB) ride @shade/transfer via userMetadata.shadeFilesWriteId
  / shadeFilesReadStreamId correlation. Server-side TransformStream
  bridges accept inbound transfers immediately (engine rejects chunks
  that arrive before accept) and park the readable for the matching
  RPC.
- Directory ops: walk(path, opts) async-iterable depth-first walker;
  uploadDirectory()/downloadDirectory() with bounded concurrency pool
  (default 4, cap 16), aggregated progress, abort.
- Production hooks (callback-based, vendor-neutral): rate-limit (op +
  byte), idempotency cache (LRU + TTL + in-flight de-dupe), path
  policy (traversal + percent-decode hardening), fingerprint gate
  (required/optional/reject), pluggable Ed25519 sig verification with
  ±5 min replay window, onMetric sink (standard names).
- React hooks (subpath @shade/files/react): ShadeFilesProvider,
  useShadeFiles, useFileList, useFileTransfer/Upload/Download.
- Shade.files.serve(handler) + Shade.files.client(peer) high-level
  entrypoint in @shade/sdk; lazy + memoized; one handler per Shade.

Wire format bump
- @shade/proto wire VERSION 0x01 → 0x02. Length prefixes changed from
  u16 to u32. The previous u16 silently truncated payloads above
  64 KiB — a hard correctness ceiling that blocked inline file ops
  up to 256 KiB. Wire-incompatible with 0.2.x peers; new sessions
  only. Cross-platform Kotlin port (android/shade-android) updated to
  match; test-vectors/wire-format.json regenerated.

Concurrency safety
- ShadeSessionManager.encrypt/.decrypt now run under per-peer mutex.
  Concurrent decryptions of the same peer raced ratchet state
  (manifested as sporadic "Failed to decrypt — wrong key or tampered
  data" under load — surfaced once concurrent uploadDirectory pumped
  many writes in flight). Encrypt was already serialized via
  Shade.send's encryptChains; decrypt is now serialized at the
  manager layer too.

@shade/streams extension
- StreamMetadata.userMetadata?: Record<string, string> for
  application-level key/value pairs that round-trip verbatim through
  stream-init plaintext. Used by @shade/files for write/read
  correlation; available to any consumer.

@shade/sdk extension
- Shade.files getter (lazy + memoized).
- BackgroundHooks.onPruneFiles + periodic timer (default 5 min) +
  BackgroundTasks.setHook(name, fn) for runtime hook registration.

Bundles in-flight 0.2.0 work
- packages/shade-streams/, packages/shade-transfer/, related
  shade-sdk streams-bridge + shade-widgets transfer hooks were
  uncommitted prior to this session. Including them keeps the
  workspace consistent at 0.3.0 since @shade/files depends on them.

Tests
- 74 new tests in @shade/files (572 → 646 workspace pass; 0 fail;
  3× stable). Coverage spans unit (inline-threshold + concurrency),
  integration (read-write inline + streams up to 1 MiB, walk +
  upload/download directory, custom-op, metrics, SDK namespace
  end-to-end), and security (tampered-envelope sig verification,
  replay window, fingerprint gate, rate-limit + quota).

Release artifacts
- All packages bumped to 0.3.0 via scripts/bump-version.ts.
- scripts/publish-all.ts PACKAGES updated with shade-files in
  topological order (after shade-transfer, before shade-sdk).
- bun run publish:dry clean (14 packed, 0 failed).
- examples/08-files-browser/ — three-process CLI demo (prekey + Bob
  server + Alice CLI) covering list/stat/mkdir/delete/upload/download.
- docs/files.md — full API + design doc.
- CHANGELOG.md 0.3.0 entry.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/shade-files/src/client/inline-threshold.ts

@@ -0,0 +1,218 @@
+/**
+ * Decide whether a write should travel inline (base64 inside the RPC
+ * envelope) or via a dedicated `@shade/transfer` stream.
+ *
+ * Threshold: 256 KiB plaintext. Anything strictly above goes through the
+ * stream path; anything ≤ goes inline.
+ *
+ * For known-size inputs (`Uint8Array`, `Blob`, `File`) the decision is
+ * cheap: compare `byteLength`/`size` against the threshold.
+ *
+ * For `ReadableStream` we cannot know the size up front. We pull chunks
+ * into a temporary buffer until we either:
+ *  - hit EOF before the threshold → inline (we have all the bytes)
+ *  - cross the threshold → streams (the buffered prefix + the rest of the
+ *    stream are returned via a fresh `ReadableStream` so the caller can
+ *    feed it to `shade.upload`).
+ */
+/** Plaintext size at which inline transitions to streams. */
+export const INLINE_THRESHOLD = 256 * 1024;
+
+export type InlineDecision =
+  | {
+      kind: 'inline';
+      bytes: Uint8Array;
+      contentType?: string;
+    }
+  | {
+      kind: 'streams';
+      stream: ReadableStream<Uint8Array>;
+      /** Plaintext size when known (Blob/File). undefined for raw streams. */
+      size?: number;
+      contentType?: string;
+    };
+
+/**
+ * Public input shape for `FileClient.write`. Runtime discriminator helper.
+ */
+export type WriteSource =
+  | Uint8Array
+  | Blob
+  | File
+  | ReadableStream<Uint8Array>
+  | { stream: ReadableStream<Uint8Array>; size: number; contentType?: string };
+
+export async function decideInline(input: WriteSource): Promise<InlineDecision> {
+  // 1. Uint8Array — direct size check
+  if (input instanceof Uint8Array) {
+    if (input.byteLength <= INLINE_THRESHOLD) {
+      return { kind: 'inline', bytes: input };
+    }
+    return {
+      kind: 'streams',
+      stream: uint8ArrayToStream(input),
+      size: input.byteLength,
+    };
+  }
+
+  // 2. Blob / File — known size (Blob.type is a string; File extends Blob)
+  if (typeof Blob !== 'undefined' && input instanceof Blob) {
+    const blob: Blob = input;
+    const contentType = blob.type === '' ? undefined : blob.type;
+    if (blob.size <= INLINE_THRESHOLD) {
+      const bytes = new Uint8Array(await blob.arrayBuffer());
+      return contentType !== undefined
+        ? { kind: 'inline', bytes, contentType }
+        : { kind: 'inline', bytes };
+    }
+    return contentType !== undefined
+      ? { kind: 'streams', stream: blob.stream(), size: blob.size, contentType }
+      : { kind: 'streams', stream: blob.stream(), size: blob.size };
+  }
+
+  // 3. Pre-wrapped { stream, size } — trust caller's declared size
+  if (
+    typeof input === 'object' &&
+    input !== null &&
+    'stream' in input &&
+    'size' in input &&
+    (input as { stream: unknown }).stream instanceof ReadableStream
+  ) {
+    const wrapped = input as { stream: ReadableStream<Uint8Array>; size: number; contentType?: string };
+    if (wrapped.size <= INLINE_THRESHOLD) {
+      const bytes = await drainStream(wrapped.stream, wrapped.size);
+      const contentType = wrapped.contentType;
+      return contentType !== undefined
+        ? { kind: 'inline', bytes, contentType }
+        : { kind: 'inline', bytes };
+    }
+    const contentType = wrapped.contentType;
+    return contentType !== undefined
+      ? { kind: 'streams', stream: wrapped.stream, size: wrapped.size, contentType }
+      : { kind: 'streams', stream: wrapped.stream, size: wrapped.size };
+  }
+
+  // 4. Bare ReadableStream — peek until threshold or EOF
+  if (input instanceof ReadableStream) {
+    return await peekStream(input);
+  }
+
+  throw new TypeError(
+    `decideInline: unsupported input type ${Object.prototype.toString.call(input)}`,
+  );
+}
+
+/**
+ * Drain a stream into a Uint8Array, with a soft cap at `expected` + slack.
+ * Used for the inline path when the caller declared a size.
+ */
+async function drainStream(
+  stream: ReadableStream<Uint8Array>,
+  expected: number,
+): Promise<Uint8Array> {
+  const reader = stream.getReader();
+  const chunks: Uint8Array[] = [];
+  let total = 0;
+  try {
+    while (true) {
+      const { value, done } = await reader.read();
+      if (done) break;
+      if (value === undefined) continue;
+      chunks.push(value);
+      total += value.byteLength;
+      if (total > expected + INLINE_THRESHOLD) {
+        throw new Error(
+          `decideInline: stream produced more bytes (${total}) than declared size (${expected})`,
+        );
+      }
+    }
+  } finally {
+    reader.releaseLock();
+  }
+  return concat(chunks, total);
+}
+
+/**
+ * Peek a `ReadableStream` of unknown length: buffer up to `INLINE_THRESHOLD + 1`
+ * bytes. If EOF first, return inline. Otherwise reconstruct a stream that
+ * yields the buffered prefix followed by the remainder.
+ */
+async function peekStream(stream: ReadableStream<Uint8Array>): Promise<InlineDecision> {
+  const reader = stream.getReader();
+  const buffered: Uint8Array[] = [];
+  let total = 0;
+  try {
+    while (total <= INLINE_THRESHOLD) {
+      const { value, done } = await reader.read();
+      if (done) {
+        reader.releaseLock();
+        return { kind: 'inline', bytes: concat(buffered, total) };
+      }
+      if (value === undefined) continue;
+      buffered.push(value);
+      total += value.byteLength;
+    }
+    // We have at least INLINE_THRESHOLD + 1 bytes buffered. Promote to streams.
+    const reconstructed = reconstructStream(buffered, reader);
+    return { kind: 'streams', stream: reconstructed };
+  } catch (err) {
+    reader.releaseLock();
+    throw err;
+  }
+}
+
+interface MinimalReader {
+  read(): Promise<{ value: Uint8Array | undefined; done: boolean }>;
+  cancel(reason?: unknown): Promise<void>;
+  releaseLock(): void;
+}
+
+function reconstructStream(
+  prefix: Uint8Array[],
+  reader: MinimalReader,
+): ReadableStream<Uint8Array> {
+  let prefixIdx = 0;
+  return new ReadableStream<Uint8Array>({
+    async pull(controller) {
+      if (prefixIdx < prefix.length) {
+        controller.enqueue(prefix[prefixIdx]!);
+        prefixIdx++;
+        return;
+      }
+      const { value, done } = await reader.read();
+      if (done) {
+        controller.close();
+        reader.releaseLock();
+        return;
+      }
+      if (value !== undefined) controller.enqueue(value);
+    },
+    async cancel(reason) {
+      try {
+        await reader.cancel(reason);
+      } finally {
+        reader.releaseLock();
+      }
+    },
+  });
+}
+
+function uint8ArrayToStream(bytes: Uint8Array): ReadableStream<Uint8Array> {
+  return new ReadableStream<Uint8Array>({
+    start(controller) {
+      controller.enqueue(bytes);
+      controller.close();
+    },
+  });
+}
+
+function concat(chunks: Uint8Array[], total: number): Uint8Array {
+  const out = new Uint8Array(total);
+  let offset = 0;
+  for (const c of chunks) {
+    out.set(c, offset);
+    offset += c.byteLength;
+  }
+  return out;
+}
+