Layer 2 MCP Watcher v0 scaffold

Per spec/agent-watcher.md §4. TypeScript/Node implementation living in
mcp-watcher/ subdirectory, parallel to Layer 1 Collector at repo root.

What lands:
- Core MCP server (src/server.ts) with experimental['claude/channel']:{}
  + tools:{} capability declarations, stdio transport, channel-event
  notifier wired through the inbox watcher.
- Identity resolution mirroring agent-ping's layered model
  (PING_AGENT_IDENTITY env, $CLAUDE_HOME/ping-agent, ~/.ping-agent).
- Inbox reader with HWM tracking, sentinel deferral (warn-after-3),
  atomic HWM writes via tmp+rename.
- chokidar-backed file watcher with coalesced drain, urgent-first
  ordering, recentEvents map for tool sender lookup.
- Three reply tools (ack / respond / mark_handled) with cross-host
  write discipline (writes to local inbox files; Syncthing replicates).
- Sentinel file (.<agent>.watcher-active) for hook coexistence per
  spec §4.3 — agent-ping hook stands down when the watcher is in
  charge of delivery on this host. Sentinel + hwm in .stignore.
- 35 unit tests passing (vitest): inbox parsing, HWM round-trip,
  sentinel deferral semantics, identity layers, tool I/O, watcher
  drain + ordering + restart-from-hwm.
- install.sh (Angus-executed, rule-2 compliant) installs deps,
  builds, symlinks ~/.local/bin/agent-watcher-mcp, prints mcp.json
  registration snippet for paste.
- README documents launch flag, sandbox CLAUDE_HOME pattern,
  hook coexistence, observability, v2 limitations.

Not yet:
- Integration test against a real Claude Code session — gated on
  Angus spinning up a sandbox CC session on the VPS with
  CLAUDE_HOME=~/.claude-sandbox.
- agent-ping hook update to read the sentinel and stand down.
  Separate small PR against agent-ping.

Interface contract with Layer 1: the inbox JSONL line shape from
inbox.ts::PingEvent matches inbox.Event in the Collector — bit-
identical reads regardless of source.

mcp-watcher/package.json

@@ -0,0 +1,32 @@
+{
+  "name": "agent-watcher-mcp",
+  "version": "0.1.0",
+  "description": "Layer 2 MCP Watcher for the agent-watcher system. Reads ping inbox files via inotify and surfaces them into a Claude Code session via Channels.",
+  "private": true,
+  "type": "module",
+  "bin": {
+    "agent-watcher-mcp": "dist/server.js"
+  },
+  "main": "dist/server.js",
+  "scripts": {
+    "build": "tsc",
+    "start": "node dist/server.js",
+    "dev": "tsx src/server.ts",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@modelcontextprotocol/sdk": "^1.0.0",
+    "chokidar": "^4.0.0"
+  },
+  "devDependencies": {
+    "@types/node": "^20.0.0",
+    "tsx": "^4.0.0",
+    "typescript": "^5.4.0",
+    "vitest": "^1.6.0"
+  },
+  "engines": {
+    "node": ">=18.0.0"
+  }
+}