docs: Update docs to reflect molecule-first paradigm (gt-nam3)

- Add molecule-first paradigm note at top of architecture.md
- Update all spawn examples to include --molecule flag
- Add "Config vs Molecule" section with cognition principle
- Add policy-to-molecule escalation note in federation-design.md
- Update role templates (mayor, witness) with molecule usage

Key message: Gas Town spawns workers on molecules, not just issues.
The issue is seed data; the molecule defines the workflow.

🤖 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

@@ -53,7 +53,7 @@ Town ({{ .TownRoot }})
 ### Work Management
 - `bd ready` - Issues ready to work (no blockers)
 - `bd list --status=open` - All open issues
-- `gt spawn --issue <id>` - Start polecat on issue
+- `gt spawn --issue <id> --molecule <mol>` - Spawn polecat with molecule workflow
 
 ### Delegation
 Prefer delegating to Refineries, not directly to polecats: