docs: add two-level beads architecture documentation

Add clear explanations of the town-level vs rig-level beads architecture:
- Town beads (~/gt/.beads): HQ coordination, no sync-branch
- Rig beads (in git clones): project work, uses beads-sync branch
- Clarify that rig-level .beads at container is gitignored

Updated:
- docs/architecture.md: New 'Two-Level Beads Architecture' section
- CLAUDE.md: Enhanced existing section with table and sync-branch info
- templates/roles/*.tmpl: Added beads architecture to crew, polecat, mayor

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -69,7 +69,18 @@ go test ./...
 
 ## Beads Database
 
-Your rig has its own beads database at `/Users/stevey/gt/gastown/.beads`
+**Two-level beads architecture** - understand this to avoid confusion:
+
+| Level | Location | sync-branch | Prefix | Purpose |
+|-------|----------|-------------|--------|---------|
+| Town | `~/gt/.beads/` | NOT set | `hq-*` | Mayor mail, HQ coordination |
+| Rig | `crew/max/.beads/` (this clone) | `beads-sync` | `gt-*` | Project issues |
+
+**Key points:**
+- You're in a **gastown.git clone** - your `.beads/` is tracked in the gastown repo
+- The rig-level `~/gt/gastown/.beads/` is **gitignored** (local runtime state)
+- Your beads sync via `beads-sync` branch to coordinate with other clones
+- Run `bd sync` to push/pull beads changes
 
 Issue prefix: `gt-`