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>

docs/streams.md

@@ -0,0 +1,117 @@
+# Shade Streams 0.2.0
+
+E2EE chunked upload/download for Shade. Drop into any Shade-using app:
+
+```ts
+const handle = await shade.upload({ to: 'bob', input: file });
+const result = await handle.done(); // { sha256, bytesSent, durationMs }
+```
+
+…and on the receiver:
+
+```ts
+shade.onIncomingTransfer(async (incoming) => {
+  const handle = await incoming.accept({ output: { kind: 'file', path: '/uploads/x' } });
+  await handle.done();
+});
+```
+
+Or in React:
+
+```tsx
+<ShadeRuntimeProvider runtime={shade}>
+  <ShadeUploader to="bob" onComplete={(r) => console.log(r.sha256)} />
+</ShadeRuntimeProvider>
+```
+
+## How it works
+
+A transfer has two planes:
+
+- **Control plane** — `stream-init`, `stream-finish`, `stream-abort`, and
+  `stream-resume-*` messages, encoded as JSON plaintext and shipped through
+  the existing Double Ratchet (envelope type `0x02`). One ratchet step
+  establishes a stream; the rest is per-chunk AEAD.
+- **Data plane** — `stream-chunk` envelopes (envelope type `0x11`),
+  AES-256-GCM-encrypted under a per-lane key, shipped over HTTP POST (or
+  WebSocket if opted-in). Lanes run in parallel for throughput.
+
+```
+Sender                                  Receiver
+──────                                  ────────
+streamSecret = randomBytes(32)
+streamId     = randomBytes(16)
+streamKey    = HKDF(streamSecret, streamId, "shade-stream/v1\0master")
+laneKey[i]   = HKDF(streamKey, streamId, "...\0lane\0" || u32(i))
+
+[stream-init JSON over Double Ratchet] ─▶
+                                          parses streamSecret, derives same keys
+                                          spawns L per-lane receivers
+
+[chunk 0x11 over HTTP]                 ─▶
+   AES-GCM(laneKey[i], plaintext, nonce=laneId||seq, aad=streamId||laneId||seq||isLast)
+                                          decrypts, verifies, writes to sink
+   (× 4 lanes in parallel)
+
+[stream-finish JSON over Double Ratchet] ─▶
+                                          verifies per-lane sha256 + overall sha256
+                                          throws TransferIntegrityError on mismatch
+```
+
+## Partition strategies
+
+- **Range** (default for known-size inputs) — lane `i` owns bytes
+  `[i·N/L, (i+1)·N/L)`. Receiver reconstructs by concatenating lane outputs
+  in laneId order.
+- **Round-robin** (default for unknown-size streams) — chunk `i` goes to
+  lane `i mod L`. Receiver reorders via a per-stream chunk-index buffer.
+
+## Resume
+
+Persistence is opt-in via a `ResumeStore` (memory, SQLite, Postgres,
+IndexedDB-ready). State persisted on init; sender's resume queries the
+receiver's `lastSeqAcked` per lane via `GET /v1/transfer/:streamId/state`,
+then continues from there. The streamSecret is encrypted at rest under a
+device-key derived from the local identity's signing private key — a
+stolen DB without the identity key cannot resume.
+
+```ts
+const handle = await shade.resumeUpload(streamId, sameInputAsBefore);
+await handle.done();
+```
+
+Resume across **identity rotation** is not supported (rotation invalidates
+the device key — by design, to prevent a stolen pre-rotation DB from
+deriving keys for any post-rotation transfer). Restart the transfer
+manually after rotation.
+
+## Throughput
+
+- Default 4 lanes × 1 MiB chunks × 4 in-flight chunks per lane =
+  16 MiB peak in-flight per direction.
+- Memory-bounded: receivers stream chunks to the configured sink without
+  buffering the full payload. 1 GB transfer = O(chunkSize) RSS, not O(file).
+- AES-GCM is hardware-accelerated via `SubtleCrypto`; SHA-256 streaming via
+  `@noble/hashes`.
+
+## Security properties
+
+| ID | Property |
+|---|---|
+| S1 | streamSecret never on the wire in plaintext (Double Ratchet only) |
+| S2 | Unique per-(streamKey, laneId, seq) AEAD nonce — no nonce reuse |
+| S3 | Tampered chunk header / ciphertext / tag → AEAD reject |
+| S4 | Per-lane sha256 + overall sha256 verified at finish |
+| S5 | streamKey/laneKey zeroized on abort/finish (`destroy()`) |
+| S6 | Concurrent streams have independent lane keys |
+| S7 | seq overflow practical-impossible (u64 max) |
+| S8 | At-rest streamSecret encrypted under device-key |
+
+## API surface
+
+See package READMEs:
+
+- `packages/shade-streams/README.md` — crypto + state machines
+- `packages/shade-transfer/README.md` — orchestration, transports, persistence
+- `packages/shade-sdk/README.md` — magic drop-in
+- `packages/shade-widgets/README.md` — React UI