feat(witness): Implement ephemeral polecat model for immediate recycling

Updates HandlePolecatDone to auto-nuke polecats immediately after MR submission
when cleanup_status=clean. This separates polecat lifecycle from MR lifecycle:

- Polecat lifecycle: spawning → working → mr_submitted → nuked
- MR lifecycle: created → queued → processed → merged (handled by Refinery)

Key changes:
- Try auto-nuke for ALL POLECAT_DONE messages regardless of MR status
- If cleanup_status=clean (branch pushed), nuke immediately
- If dirty state, create cleanup wisp for manual intervention
- Cleanup wisps are now exception handling, not the normal flow

Conflict resolution is handled by the Refinery, which creates NEW tasks
for NEW polecats when merge conflicts are detected.

(gt-si8rq.9)

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

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

internal/witness/handlers.go

@@ -29,7 +29,14 @@ type HandlerResult struct {
 // HandlePolecatDone processes a POLECAT_DONE message from a polecat.
 // For ESCALATED/DEFERRED exits (no pending MR), auto-nukes if clean.
 // For PHASE_COMPLETE exits, recycles the polecat (session ends, worktree kept).
-// For exits with pending MR, creates a cleanup wisp to wait for MERGED.
+// For COMPLETED exits with MR and clean state, auto-nukes immediately (ephemeral model).
+// For exits with pending MR but dirty state, creates cleanup wisp for manual intervention.
+//
+// Ephemeral Polecat Model:
+// Polecats are truly ephemeral - done at MR submission, recyclable immediately.
+// Once the branch is pushed (cleanup_status=clean), the polecat can be nuked.
+// The MR lifecycle continues independently in the Refinery.
+// If conflicts arise, Refinery creates a NEW conflict-resolution task for a NEW polecat.
 func HandlePolecatDone(workDir, rigName string, msg *mail.Message) *HandlerResult {
 	result := &HandlerResult{
 		MessageID:    msg.ID,
@@ -59,23 +66,28 @@ func HandlePolecatDone(workDir, rigName string, msg *mail.Message) *HandlerResul
 	// ESCALATED/DEFERRED exits typically have no MR pending
 	hasPendingMR := payload.MRID != "" || payload.Exit == "COMPLETED"
 
-	if !hasPendingMR {
+	// Ephemeral model: try to auto-nuke immediately regardless of MR status
-		// No MR pending - can auto-nuke immediately if clean
+	// If cleanup_status is clean, the branch is pushed and polecat is recyclable.
-		nukeResult := AutoNukeIfClean(workDir, rigName, payload.PolecatName)
+	// The MR will be processed independently by the Refinery.
-		if nukeResult.Nuked {
+	nukeResult := AutoNukeIfClean(workDir, rigName, payload.PolecatName)
-			result.Handled = true
+	if nukeResult.Nuked {
+		result.Handled = true
+		if hasPendingMR {
+			// Ephemeral model: polecat nuked, MR continues in Refinery
+			result.Action = fmt.Sprintf("auto-nuked %s (ephemeral: exit=%s, MR=%s): %s", payload.PolecatName, payload.Exit, payload.MRID, nukeResult.Reason)
+		} else {
 			result.Action = fmt.Sprintf("auto-nuked %s (exit=%s, no MR): %s", payload.PolecatName, payload.Exit, nukeResult.Reason)
-			return result
 		}
-		if nukeResult.Error != nil {
+		return result
-			// Nuke failed - fall through to create wisp for manual cleanup
+	}
-			result.Error = nukeResult.Error
+	if nukeResult.Error != nil {
-		}
+		// Nuke failed - fall through to create wisp for manual cleanup
-		// Couldn't auto-nuke (dirty state or verification failed) - create wisp for manual intervention
+		result.Error = nukeResult.Error
 	}
 
-	// Create a cleanup wisp for this polecat
+	// Couldn't auto-nuke (dirty state or verification failed) - create wisp for manual intervention
-	// Either waiting for MR to be merged, or needs manual cleanup
+	// Note: Even with pending MR, if we can't auto-nuke it means something is wrong
+	// (uncommitted changes, unpushed commits, etc.) that needs attention.
 	wispID, err := createCleanupWisp(workDir, payload.PolecatName, payload.IssueID, payload.Branch)
 	if err != nil {
 		result.Error = fmt.Errorf("creating cleanup wisp: %w", err)
@@ -85,9 +97,9 @@ func HandlePolecatDone(workDir, rigName string, msg *mail.Message) *HandlerResul
 	result.Handled = true
 	result.WispCreated = wispID
 	if hasPendingMR {
-		result.Action = fmt.Sprintf("created cleanup wisp %s for %s (waiting for MR %s)", wispID, payload.PolecatName, payload.MRID)
+		result.Action = fmt.Sprintf("created cleanup wisp %s for %s (MR=%s, needs intervention: %s)", wispID, payload.PolecatName, payload.MRID, nukeResult.Reason)
 	} else {
-		result.Action = fmt.Sprintf("created cleanup wisp %s for %s (needs manual cleanup: dirty state)", wispID, payload.PolecatName)
+		result.Action = fmt.Sprintf("created cleanup wisp %s for %s (needs manual cleanup: %s)", wispID, payload.PolecatName, nukeResult.Reason)
 	}
 
 	return result