fix(ingestion): close the PR #152 review findings on REST auth

- main.go's wiring was untested (the test built its own copy of the
  router, so dropping auth in main or re-registering POST /query as
  public stayed green). Routing is now one function, buildMux, which
  main calls and the tests call: it constructs the bearer middleware
  itself, registers public handlers only for patterns on a fixed
  allowlist (a public REST pattern would beat the authenticated
  catch-all by specificity), refuses an empty token, and returns an
  http.Handler so nothing can add a route to the result.
- hyperguild CLI: PassRate sent no token and would 401. Every request
  now goes through brainClient.do, which adds it; the test covers
  Query, Write and PassRate and is named for that.
- ResolveIngestPath returns one refusal for every bad path; the raw
  EvalSymlinks error let a caller probe which server files exist and
  leaked the brain directory.
- PROJECT.md (and derived adapters) and the pass-rate runbook state
  that the REST API needs BRAIN_MCP_TOKEN and is tailnet/in-cluster.

Refs #149

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/runbooks/exercising-pass-rate-traffic.md

@@ -24,7 +24,7 @@ Only a `tools/call` to the routing pod records a pass/fail.
 |---------|-----|------|
 | Routing MCP (local, Tailscale) | `http://koala:30310/mcp` | Bearer `ROUTING_MCP_TOKEN` |
 | Routing MCP (remote) | `https://routing-mcp.d-ma.be/mcp` | OAuth via `auth.d-ma.be` (audience `claude-ai`) |
-| Pass-rate readout | `http://koala:30330/pass-rate?skill=<name>` | none (read-only) |
+| Pass-rate readout | `http://koala:30330/pass-rate?skill=<name>` | Bearer `BRAIN_MCP_TOKEN` (since hyperguild#149) |
 
 Tools advertised: **`review`**, **`debug`** (the two the #35 gate measures),
 plus `session_log`, `retrospective`, `trainer`.