docs: improve help text and add nudge documentation

Polish help text across all agent commands to clarify roles:
- crew: persistent workspaces vs ephemeral polecats
- deacon: town-level watchdog receiving heartbeats
- dog: cross-rig infrastructure workers (cats vs dogs)
- mayor: Chief of Staff for cross-rig coordination
- nudge: universal synchronous messaging API
- polecat: ephemeral one-task workers, self-cleaning
- refinery: merge queue serializer per rig
- witness: per-rig polecat health monitor

Add comprehensive gt nudge documentation to crew template explaining
when to use nudge vs mail, common patterns, and target shortcuts.

Add orphan-process-cleanup step to deacon patrol formula to clean up
claude subagent processes that fail to exit (TTY = "?").

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

internal/cmd/witness.go

@@ -24,16 +24,23 @@ var (
 var witnessCmd = &cobra.Command{
 	Use:     "witness",
 	GroupID: GroupAgents,
-	Short:   "Manage the polecat monitoring agent",
+	Short:   "Manage the Witness (per-rig polecat health monitor)",
 	RunE:    requireSubcommand,
-	Long: `Manage the Witness monitoring agent for a rig.
+	Long: `Manage the Witness - the per-rig polecat health monitor.
 
-The Witness monitors polecats for stuck states and orphaned sandboxes,
-nudges polecats that seem blocked, and reports status to the mayor.
+The Witness patrols a single rig, watching over its polecats:
+  - Detects stalled polecats (crashed or stuck mid-work)
+  - Nudges unresponsive sessions back to life
+  - Cleans up zombie polecats (finished but failed to exit)
+  - Nukes sandboxes when polecats complete via 'gt done'
 
-In the self-cleaning model, polecats nuke themselves after work completion.
-The Witness handles edge cases: crashed sessions, orphaned worktrees, and
-stuck polecats that need intervention.`,
+The Witness does NOT force session cycles or interrupt working polecats.
+Polecats manage their own sessions (via gt handoff). The Witness handles
+failures and edge cases only.
+
+One Witness per rig. The Deacon monitors all Witnesses.
+
+Role shortcuts: "witness" in mail/nudge addresses resolves to this rig's Witness.`,
 }
 
 var witnessStartCmd = &cobra.Command{