feat(v0.6): route lease-freshness callsites through IsStale

InspectLease, CleanupStaleLease, runActiveLeaseCheck, and statusAt now
use the PID-aware IsStale predicate. A dead local owner PID makes a lease
stale immediately; SessionStatus / list / info reflect this with no
display-code change.

Corrects three cmd-package session-display test fixtures that built
"active" leases with the local hostname but synthetic PIDs — now that
freshness is PID-aware, an active session must be owned by a live
process, so the fixtures use os.Getpid().

cmd/info_session_test.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"encoding/json"
+	"fmt"
 	"os"
 	"path/filepath"
 	"strings"
@@ -61,8 +62,12 @@ func TestInfoShowsActivePersistentSessionWithAttachHint(t *testing.T) {
 	wsDir := makeInfoSessionWorkspace(t, root, "active-persist")
 
 	now := time.Now().UTC().Truncate(time.Second)
+	// An active session is owned by a live process: lease freshness is
+	// PID-aware (v0.6 Phase 3), so a local-hostname lease must point at a
+	// live PID to read as active. Use the test process itself.
+	livePID := os.Getpid()
 	writeLeaseAtForCmdTest(t, wsDir, &session.Lease{
-		PID:             12345,
+		PID:             livePID,
 		Hostname:        session.CurrentHostname(),
 		Mode:            "persistent",
 		StartedAt:       now,
@@ -76,7 +81,7 @@ func TestInfoShowsActivePersistentSessionWithAttachHint(t *testing.T) {
 	for _, want := range []string{
 		"Session:      active",
 		"Mode:       persistent",
-		"Owner:      pid 12345", // local host -> hostname omitted
+		fmt.Sprintf("Owner:      pid %d", livePID), // local host -> hostname omitted
 		"Attach:     ctask attach active-persist",
 	} {
 		if !strings.Contains(out, want) {
@@ -91,8 +96,10 @@ func TestInfoShowsActiveDirectSessionWithoutAttachHint(t *testing.T) {
 	wsDir := makeInfoSessionWorkspace(t, root, "active-direct")
 
 	now := time.Now().UTC().Truncate(time.Second)
+	// Live PID required for an active local-hostname lease — see
+	// TestInfoShowsActivePersistentSessionWithAttachHint.
 	writeLeaseAtForCmdTest(t, wsDir, &session.Lease{
-		PID:             8888,
+		PID:             os.Getpid(),
 		Hostname:        session.CurrentHostname(),
 		Mode:            "direct",
 		StartedAt:       now,

cmd/list_session_test.go

@@ -47,17 +47,25 @@ func TestListSessionColumnShowsModeAndStaleAndDash(t *testing.T) {
 	staleWS := makeListSessionWorkspace(t, root, "general", "2026-05-12_stale-ws", "stale-ws", "active")
 	makeListSessionWorkspace(t, root, "general", "2026-05-11_idle-ws", "idle-ws", "active")
 
+	// persist-ws and direct-ws must read as active sessions: a fresh
+	// heartbeat alone is not enough now that lease freshness is PID-aware
+	// (v0.6 Phase 3). Use the live test process PID so the local-hostname
+	// lease passes the PID-liveness check, mirroring
+	// session.TestInspectLeaseFreshLocal.
+	livePID := os.Getpid()
 	writeLeaseAtForCmdTest(t, persistWS, &session.Lease{
-		PID: 1, Hostname: host, Mode: "persistent",
+		PID: livePID, Hostname: host, Mode: "persistent",
 		StartedAt: now, LastHeartbeatAt: now,
 	})
 	writeLeaseAtForCmdTest(t, directWS, &session.Lease{
-		PID: 2, Hostname: host, Mode: "direct",
+		PID: livePID, Hostname: host, Mode: "direct",
 		StartedAt: now, LastHeartbeatAt: now,
 	})
+	// stale-ws is wall-clock stale (heartbeat 10m ago); its PID is
+	// irrelevant — wall-clock staleness wins unconditionally.
 	heartbeat := now.Add(-10 * time.Minute)
 	writeLeaseAtForCmdTest(t, staleWS, &session.Lease{
-		PID: 3, Hostname: host, Mode: "direct",
+		PID: livePID, Hostname: host, Mode: "direct",
 		StartedAt: heartbeat, LastHeartbeatAt: heartbeat,
 	})