feat: Add automatic orphaned claude process cleanup (#588)

* feat: Add automatic orphaned claude process cleanup

Claude Code's Task tool spawns subagent processes that sometimes don't clean up
properly after completion. These accumulate and consume significant memory
(observed: 17 processes using ~6GB RAM).

This change adds automatic cleanup in two places:

1. **Deacon patrol** (primary): New patrol step "orphan-process-cleanup" runs
   `gt deacon cleanup-orphans` early in each cycle. More responsive (~30s).

2. **Daemon heartbeat** (fallback): Runs cleanup every 3 minutes as safety net
   when deacon is down.

Detection uses TTY column - processes with TTY "?" have no controlling terminal.
This is safe because:
- Processes in terminals (user sessions) have a TTY like "pts/0" - untouched
- Only kills processes with no controlling terminal
- Orphaned subagents are children of tmux server with no TTY

New files:
- internal/util/orphan.go: FindOrphanedClaudeProcesses, CleanupOrphanedClaudeProcesses
- internal/util/orphan_test.go: Tests for orphan detection

New command:
- `gt deacon cleanup-orphans`: Manual/patrol-triggered cleanup

Fixes #587

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

* fix(orphan): add Windows build tag and minimum age check

Addresses review feedback on PR #588:

1. Add //go:build !windows to orphan.go and orphan_test.go
   - The code uses Unix-specific syscalls (SIGTERM, ESRCH) and
     ps command options that don't exist on Windows

2. Add minimum age check (60 seconds) to prevent false positives
   - Prevents race conditions with newly spawned subagents
   - Addresses reviewer concern about cron/systemd processes
   - Uses portable etime format instead of Linux-only etimes

3. Add parseEtime helper with comprehensive tests
   - Parses [[DD-]HH:]MM:SS format (works on both Linux and macOS)
   - etimes (seconds) is Linux-specific, etime is portable

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

* fix(orphan): add proper SIGTERM→SIGKILL escalation with state tracking

Previous approach used process age which doesn't work: a Task subagent
runs without TTY from birth, so a long-running legitimate subagent that
later fails to exit would be immediately SIGKILLed without trying SIGTERM.

New approach uses a state file to track signal history:

1. First encounter → SIGTERM, record PID + timestamp in state file
2. Next cycle (after 60s grace period) → if still alive, SIGKILL
3. Next cycle → if survived SIGKILL, log as unkillable and remove

State file: $XDG_RUNTIME_DIR/gastown-orphan-state (or /tmp/)
Format: "<pid> <signal> <unix_timestamp>" per line

The state file is automatically cleaned up:
- Dead processes removed on load
- Unkillable processes removed after logging

Also updates callers to use new CleanupResult type which includes
the signal sent (SIGTERM, SIGKILL, or UNKILLABLE).

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

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

internal/daemon/daemon.go

@@ -28,6 +28,7 @@ import (
 	"github.com/steveyegge/gastown/internal/rig"
 	"github.com/steveyegge/gastown/internal/session"
 	"github.com/steveyegge/gastown/internal/tmux"
+	"github.com/steveyegge/gastown/internal/util"
 	"github.com/steveyegge/gastown/internal/wisp"
 	"github.com/steveyegge/gastown/internal/witness"
 )
@@ -268,6 +269,11 @@ func (d *Daemon) heartbeat(state *State) {
 	// This validates tmux sessions are still alive for polecats with work-on-hook
 	d.checkPolecatSessionHealth()
 
+	// 12. Clean up orphaned claude subagent processes (memory leak prevention)
+	// These are Task tool subagents that didn't clean up after completion.
+	// This is a safety net - Deacon patrol also does this more frequently.
+	d.cleanupOrphanedProcesses()
+
 	// Update state
 	state.LastHeartbeat = time.Now()
 	state.HeartbeatCount++
@@ -980,3 +986,26 @@ Manual intervention may be required.`,
 		d.logger.Printf("Warning: failed to notify witness of crashed polecat: %v", err)
 	}
 }
+
+// cleanupOrphanedProcesses kills orphaned claude subagent processes.
+// These are Task tool subagents that didn't clean up after completion.
+// Detection uses TTY column: processes with TTY "?" have no controlling terminal.
+// This is a safety net fallback - Deacon patrol also runs this more frequently.
+func (d *Daemon) cleanupOrphanedProcesses() {
+	results, err := util.CleanupOrphanedClaudeProcesses()
+	if err != nil {
+		d.logger.Printf("Warning: orphan process cleanup failed: %v", err)
+		return
+	}
+
+	if len(results) > 0 {
+		d.logger.Printf("Orphan cleanup: processed %d process(es)", len(results))
+		for _, r := range results {
+			if r.Signal == "UNKILLABLE" {
+				d.logger.Printf("  WARNING: PID %d (%s) survived SIGKILL", r.Process.PID, r.Process.Cmd)
+			} else {
+				d.logger.Printf("  Sent %s to PID %d (%s)", r.Signal, r.Process.PID, r.Process.Cmd)
+			}
+		}
+	}
+}