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/witness.md.tmpl

@@ -76,6 +76,8 @@ bd show <id>                             # Issue details
 bd list --status=in_progress             # Active work in rig
 ```
 
+**Prefix-based routing:** `bd show gt-xyz` works from anywhere - routes via `~/gt/.beads/routes.jsonl`.
+
 ---
 
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