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-core/src/session.ts

@@ -23,9 +23,8 @@ import {
   ratchetEncrypt,
   ratchetDecrypt,
 } from './ratchet.js';
-import { NoSessionError, UntrustedIdentityError } from './errors.js';
+import { NoSessionError } from './errors.js';
 import { computeFingerprint, shortFingerprint } from './fingerprint.js';
-import { constantTimeEqual } from './crypto.js';
 import { ShadeEventEmitter, shortHash } from './events.js';
 
 const enc = new TextEncoder();
@@ -61,13 +60,42 @@ export class ShadeSessionManager {
   private registrationId: number = 0;
   private currentSignedPreKeyId: number = 0;
   private readonly events?: ShadeEventEmitter;
+  /**
+   * Per-address operation chain. Both encrypt and decrypt mutate ratchet
+   * state in place (counter, DH key, skipped-keys cache); concurrent
+   * operations on the same peer can corrupt the session. We serialize
+   * per-peer by chaining promises — operations to different peers stay
+   * fully concurrent.
+   */
+  private readonly peerOpChains = new Map<string, Promise<unknown>>();
 
   constructor(
     private readonly crypto: CryptoProvider,
     private readonly storage: StorageProvider,
     options: { events?: ShadeEventEmitter } = {},
   ) {
-    this.events = options.events;
+    if (options.events !== undefined) {
+      this.events = options.events;
+    }
+  }
+
+  /**
+   * Run `fn` under the per-address mutex so encrypt/decrypt for the same
+   * peer never interleave their session-state mutations.
+   */
+  private async runUnderPeerLock<T>(address: string, fn: () => Promise<T>): Promise<T> {
+    const previous = this.peerOpChains.get(address) ?? Promise.resolve();
+    const next = previous.catch(() => undefined).then(fn);
+    this.peerOpChains.set(address, next);
+    try {
+      return await next;
+    } finally {
+      // Best-effort cleanup so finished chains can be garbage collected
+      // when a peer goes idle. If a newer op has chained on, we leave it.
+      if (this.peerOpChains.get(address) === next) {
+        this.peerOpChains.delete(address);
+      }
+    }
   }
 
   /** Get the event emitter (if observability is enabled) */
@@ -368,56 +396,60 @@ export class ShadeSessionManager {
    * Subsequent messages are standard RatchetMessages.
    */
   async encrypt(address: string, plaintext: string): Promise<ShadeEnvelope> {
-    const session = await this.storage.getSession(address);
-    if (!session) throw new NoSessionError(address);
+    return this.runUnderPeerLock(address, async () => {
+      const session = await this.storage.getSession(address);
+      if (!session) throw new NoSessionError(address);
 
-    const ratchetMsg = await ratchetEncrypt(this.crypto, session, enc.encode(plaintext));
+      const ratchetMsg = await ratchetEncrypt(this.crypto, session, enc.encode(plaintext));
 
-    this.events?.emit('message.encrypted', {
-      address,
-      counter: ratchetMsg.counter,
-      ciphertextSize: ratchetMsg.ciphertext.length,
-    });
+      this.events?.emit('message.encrypted', {
+        address,
+        counter: ratchetMsg.counter,
+        ciphertextSize: ratchetMsg.ciphertext.length,
+      });
+
+      // Check if this is the first message (X3DH metadata attached)
+      const x3dh = (session as any).__x3dh;
+      if (x3dh) {
+        delete (session as any).__x3dh;
+        await this.storage.saveSession(address, session);
+
+        const preKeyMsg: PreKeyMessage = {
+          registrationId: x3dh.registrationId,
+          preKeyId: x3dh.preKeyId,
+          signedPreKeyId: x3dh.signedPreKeyId,
+          ephemeralKey: x3dh.ephemeralPublicKey,
+          identityDHKey: x3dh.identityDHKey,
+          message: ratchetMsg,
+        };
+        return {
+          type: 'prekey',
+          content: preKeyMsg,
+          timestamp: Date.now(),
+          senderAddress: address,
+        };
+      }
 
-    // Check if this is the first message (X3DH metadata attached)
-    const x3dh = (session as any).__x3dh;
-    if (x3dh) {
-      delete (session as any).__x3dh;
       await this.storage.saveSession(address, session);
-
-      const preKeyMsg: PreKeyMessage = {
-        registrationId: x3dh.registrationId,
-        preKeyId: x3dh.preKeyId,
-        signedPreKeyId: x3dh.signedPreKeyId,
-        ephemeralKey: x3dh.ephemeralPublicKey,
-        identityDHKey: x3dh.identityDHKey,
-        message: ratchetMsg,
-      };
       return {
-        type: 'prekey',
-        content: preKeyMsg,
+        type: 'ratchet',
+        content: ratchetMsg,
         timestamp: Date.now(),
         senderAddress: address,
       };
-    }
-
-    await this.storage.saveSession(address, session);
-    return {
-      type: 'ratchet',
-      content: ratchetMsg,
-      timestamp: Date.now(),
-      senderAddress: address,
-    };
+    });
   }
 
   /**
    * Decrypt a message from a peer. Handles both PreKeyMessage and RatchetMessage.
    */
   async decrypt(address: string, envelope: ShadeEnvelope): Promise<string> {
-    if (envelope.type === 'prekey') {
-      return this.decryptPreKeyMessage(address, envelope.content as PreKeyMessage);
-    }
-    return this.decryptRatchetMessage(address, envelope.content as RatchetMessage);
+    return this.runUnderPeerLock(address, async () => {
+      if (envelope.type === 'prekey') {
+        return this.decryptPreKeyMessage(address, envelope.content as PreKeyMessage);
+      }
+      return this.decryptRatchetMessage(address, envelope.content as RatchetMessage);
+    });
   }
 
   private async decryptPreKeyMessage(address: string, message: PreKeyMessage): Promise<string> {