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/protocol/envelope-codec.ts

@@ -0,0 +1,70 @@
+import { z } from 'zod';
+import {
+  RpcCancelSchema,
+  RpcErrorSchema,
+  RpcRequestSchema,
+  RpcResponseSchema,
+  type RpcCancel,
+  type RpcEnvelope,
+  type RpcError,
+  type RpcRequest,
+  type RpcResponse,
+} from '../schemas/envelope.js';
+import { KIND_PREFIX } from './version.js';
+
+/** Tagged classification of any incoming envelope. */
+export type ClassifiedEnvelope =
+  | { kind: 'request'; envelope: RpcRequest }
+  | { kind: 'response'; envelope: RpcResponse }
+  | { kind: 'error'; envelope: RpcError }
+  | { kind: 'cancel'; envelope: RpcCancel };
+
+const RpcAnySchema = z.union([
+  RpcRequestSchema,
+  RpcResponseSchema,
+  RpcErrorSchema,
+  RpcCancelSchema,
+]);
+
+/** Encode an envelope to JSON plaintext for `Shade.send`. */
+export function encodeEnvelope(env: RpcEnvelope): string {
+  return JSON.stringify(env);
+}
+
+/**
+ * Quick-detection: does this plaintext look like an `@shade/files` envelope?
+ * Used by `ShadeFileRpcChannel` to skip non-files messages cheaply.
+ */
+export function looksLikeFileEnvelope(plaintext: string): boolean {
+  return plaintext.includes(KIND_PREFIX);
+}
+
+/**
+ * Parse and classify an incoming plaintext. Returns null on any malformed
+ * input — the channel ignores those silently (could be a different
+ * protocol on the same Shade.send pipe).
+ */
+export function tryParseEnvelope(plaintext: string): ClassifiedEnvelope | null {
+  let raw: unknown;
+  try {
+    raw = JSON.parse(plaintext);
+  } catch {
+    return null;
+  }
+  const result = RpcAnySchema.safeParse(raw);
+  if (!result.success) return null;
+  return classify(result.data);
+}
+
+export function classify(env: RpcEnvelope): ClassifiedEnvelope {
+  if (env.kind === 'shade.fs.cancel/v1') {
+    return { kind: 'cancel', envelope: env as RpcCancel };
+  }
+  if (env.kind === 'shade.fs.error/v1') {
+    return { kind: 'error', envelope: env as RpcError };
+  }
+  if (env.kind.endsWith('.response')) {
+    return { kind: 'response', envelope: env as RpcResponse };
+  }
+  return { kind: 'request', envelope: env as RpcRequest };
+}