P1 spine: monorepo, shared WS protocol, server daemon

- npm workspaces (shared / server / web), TS strict, project refs
- @arboretum/shared: multiplexed WS protocol (JSON control + binary
  output frames: 1B type + u32le channel), flow-control constants
  (ACK 256K, HIGH 384K, LOW 128K, lagging 2M), REST types
- git-arboretum server: Fastify 5 + node:sqlite (single native dep:
  node-pty prebuilt), token auth (sha256 at rest, HMAC cookie, global
  login rate limit + backoff), strict Origin check on /api and /ws,
  PtyManager (2MiB ring with monotonic offset, resync replay = reset +
  256KiB tail, pause/resume only when ALL interactive clients exceed
  HIGH, observers never throttle, lagging clients resync), WS gateway
  (attach/stdin/resize/ack, heartbeat 30s), SIGTERM→SIGKILL 5s grace
- CLI: arboretum [--port 7317] [--bind 127.0.0.1] — non-loopback bind
  requires an explicit safety flag
- Smoke-tested: login/401/403-origin/spawn bash/kill/grace-SIGKILL all
  green

packages/shared/tsconfig.json

@@ -0,0 +1,8 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "rootDir": "src",
+    "outDir": "dist"
+  },
+  "include": ["src"]
+}