feat: Add rig infra cycling (witness ↔ refinery)

Extended the unified cycle system to include rig infrastructure sessions:
- Witness ↔ Refinery (per rig) now cycle with C-b n/p

Also moved SetCycleBindings into ConfigureGasTownSession so ALL Gas Town
sessions automatically get the unified cycle bindings. Removed redundant
individual calls from crew, mayor, and deacon startup code.

Cycle groups are now:
- Town: Mayor ↔ Deacon
- Crew (per rig): All crew members in same rig
- Infra (per rig): Witness ↔ Refinery

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

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

internal/cmd/mayor.go

@@ -123,12 +123,10 @@ func startMayorSession(t *tmux.Tmux) error {
 	_ = t.SetEnvironment(MayorSessionName, "BD_ACTOR", "mayor")
 
 	// Apply Mayor theme (non-fatal: theming failure doesn't affect operation)
+	// Note: ConfigureGasTownSession includes cycle bindings
 	theme := tmux.MayorTheme()
 	_ = t.ConfigureGasTownSession(MayorSessionName, theme, "", "Mayor", "coordinator")
 
-	// Set up C-b n/p keybindings for town session cycling (non-fatal)
-	_ = t.SetTownCycleBindings(MayorSessionName)
-
 	// Launch Claude - the startup hook handles 'gt prime' automatically
 	// Use SendKeysDelayed to allow shell initialization after NewSession
 	// Export GT_ROLE and BD_ACTOR in the command since tmux SetEnvironment only affects new panes