refactor: extract agent bounded context + fix SSE comments + cleanup unused

- Extract src/lib/agent/ bounded context with types, registry, messaging
- Add comments_count to BeadIssue for SSE comment detection
- Create batch endpoints for mail/reservations APIs
- Add memory validation to session-preflight
- Remove unused empty dirs (mockup, sessions, timeline)
- Move stashes to docs/references, gitignore them

project.md

@@ -0,0 +1,80 @@
+# project.md — BeadBoard Driver Session Cache
+
+This file is maintained by agents. A new agent reads this first.
+If the Environment Status table shows all `pass`, skip straight to Step 2 of the runbook.
+Only re-run a check if its row says `fail` or `unknown`, or if you hit an actual error.
+
+---
+
+## Environment Status Cache
+
+Last updated: YYYY-MM-DD by `<agent-bead-id>`
+
+| Component | Status | Version / Detail | Verified |
+|-----------|--------|-----------------|---------|
+| `bd` on PATH | `unknown` | | |
+| `bb` on PATH | `unknown` | | |
+| `.beads` db exists | `unknown` | | |
+| `mail.delegate` configured | `unknown` | | |
+| `session-preflight` | `unknown` | | |
+| `bb agent` registered | `unknown` | `BB_AGENT=` | |
+| Tests last run | `unknown` | | |
+
+**Status values:** `pass` · `fail` · `unknown` · `skip` (not applicable to this project)
+
+**Rule:** If every row is `pass` → skip Step 1 entirely and go straight to Step 2.
+If any row is `fail` or `unknown` → run only that check, update this table, continue.
+
+---
+
+## Project Identity
+
+- Project name:
+- Repository root:
+- Primary language/runtime:
+- Primary package manager:
+
+## Tooling Baseline
+
+- `bd` installed and on PATH: yes/no — version:
+- `bb` installed and on PATH: yes/no — version:
+- Detection commands used:
+- Shell/platform: (e.g. WSL2/bash, macOS/zsh, Windows/PowerShell)
+
+## BeadBoard/Communication Setup
+
+- `.beads` database: exists/created on YYYY-MM-DD via `bd init`
+- Mail delegate: `bd config set mail.delegate "node <abs-path>/scripts/bb-mail-shim.mjs"` — configured YYYY-MM-DD
+- Agent identity policy: `export BB_AGENT=<role-name>` (set fresh each session in Step 2)
+- `session-preflight` last pass: YYYY-MM-DD
+
+## Agent State + Heartbeat Policy
+
+- Agent bead naming: `bb-<role-name>` (e.g. `bb-silver-scribe`)
+- Required state transitions: `spawning → running → working → stuck/done/stopped`
+- Heartbeat: LLM agents heartbeat at turn start + before long commands; daemon agents every 5 min
+
+## Command Baseline
+
+- Install:
+- Build:
+- Typecheck:
+- Lint:
+- Test:
+
+## Known Workarounds
+
+Document only stable, repeatable workarounds.
+
+1. Trigger:
+   - Symptom:
+   - Workaround:
+   - Verified:
+
+## Session Log (append-only)
+
+Each agent appends one line when they update this file:
+
+| Date | Agent | What changed |
+|------|-------|-------------|
+| YYYY-MM-DD | `<agent-bead-id>` | Initial project.md created |