fix(infra): unblock docker builds for stars agent and web

- Dockerfile.ml: install build-essential so pyswisseph (stars agent) compiles
- Dockerfile.web: copy root package.json + pnpm-workspace.yaml + pnpm-lock.yaml into builder stage so pnpm --filter resolves the workspace
- CLAUDE.md: record both gotchas alongside the existing Docker rebuild notes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -71,6 +71,8 @@ docs/              architecture notes, ADRs, API specs
   - **Never run two `docker compose up --build` at once** — both grab the same `--mount=type=cache,id=pnpm` and deadlock on the API's `pnpm --prod deploy` step. Symptom: build sits silent for hours on `[api builder 8/8]`. Before starting any build, check `ps aux | grep "docker compose"` and kill any prior `up --build` (`kill -9 <pid>` — the wrapper bash and the docker compose binary are separate PIDs; kill the docker compose one).
   - **Don't add `--offline` to `pnpm --prod deploy`** — pnpm's metadata cache (`/root/.cache/pnpm/`) is not in the `/pnpm/store` cache mount, so `--offline` fails with `ERR_PNPM_NO_OFFLINE_META` for transitive devDeps (e.g. vite via vitest). Leave the deploy step network-on; it works.
   - **All TS Dockerfiles need `python3 make g++`** in the base stage — `better-sqlite3` rebuilds natively on install. Missing from `Dockerfile.admin` historically caused `gyp ERR! find Python` failures.
+  - **`Dockerfile.ml` needs `build-essential`** (not just `gcc`) — `pyswisseph` (stars agent) compiles C from source and fails with `fatal error: math.h: No such file or directory` if only `gcc` is installed; it needs `libc-dev` too, easiest via `build-essential`.
+  - **`Dockerfile.web` builder stage needs root `package.json` + `pnpm-workspace.yaml` + `pnpm-lock.yaml`** copied in. Without them, `pnpm --filter @oo/shared-types build` fails with `[ERR_PNPM_NO_PKG_MANIFEST] No package.json found in /app`. The deps stage has them but the builder is a fresh layer; selective copies must include them.
   - **A clean build of `--profile core` takes ~3 min total** when the buildx cache is warm. If it's been silent for >10 min, check for the parallel-build deadlock above before assuming "still going".
 - Run Python agent tests: `python3 -m pytest ml/agents/tests/ -x -q` (tests add repo root to `sys.path` themselves).
 - Run Python feature tests: `python3 -m pytest ml/features/ -x -q`