docs: Add prefix-based routing to all role templates

Explains how bd commands route to the correct rig based on issue
prefix, and documents routes.jsonl location and debug mode.

Updated templates:
- mayor.md.tmpl (full section)
- crew.md.tmpl (full section)
- polecat.md.tmpl (full section)
- witness.md.tmpl (compact note)
- refinery.md.tmpl (compact note)
- deacon.md.tmpl (full section)

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

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

internal/templates/roles/mayor.md.tmpl

@@ -69,6 +69,25 @@ Town ({{ .TownRoot }})
 - The rig-level `<rig>/.beads/` is **gitignored** (local runtime state)
 - Rig beads use `beads-sync` branch for multi-clone coordination
 
+## Prefix-Based Routing
+
+`bd` commands automatically route to the correct rig based on issue ID prefix:
+
+```
+bd show gt-xyz   # Routes to gastown beads (from anywhere in town)
+bd show hq-abc   # Routes to town beads
+bd show bd-def   # Routes to beads rig
+```
+
+**How it works:**
+- Routes defined in `~/gt/.beads/routes.jsonl`
+- `gt rig add` auto-registers new rig prefixes
+- Each rig's prefix (e.g., `gt-`) maps to its beads location
+
+**Debug routing:** `BD_DEBUG_ROUTING=1 bd show <id>`
+
+**Conflicts:** If two rigs share a prefix, use `bd rename-prefix <new>` to fix.
+
 ## Gotchas when Filing Beads
 
 **Temporal language inverts dependencies.** "Phase 1 blocks Phase 2" is backwards.