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().

internal/session/adopt_pidcheck_test.go

@@ -0,0 +1,45 @@
+package session
+
+import (
+	"testing"
+	"time"
+)
+
+// A fresh-by-wall-clock local lease whose owner PID is dead must be
+// classified LeaseStateStale by InspectLease, so the persistent-mode
+// dispatcher routes to adoption immediately rather than after the 60s
+// wall-clock wait. (dispatchPersistent itself lives in cmd/ and is
+// covered there; this test pins the InspectLease half of the contract.)
+func TestInspectLeaseDeadLocalPIDIsStale(t *testing.T) {
+	withCheckProcess(t, func(int) ProcessState { return ProcessDead })
+	ws := t.TempDir()
+	now := time.Now().UTC()
+	writeLeaseAt(t, ws, &Lease{
+		SessionID:       "test",
+		PID:             4242,
+		Hostname:        currentHostname(),
+		LastHeartbeatAt: now, // fresh by wall-clock
+		StartedAt:       now,
+	})
+	if got := InspectLease(ws); got != LeaseStateStale {
+		t.Errorf("dead-PID local lease: InspectLease = %v, want LeaseStateStale", got)
+	}
+}
+
+// The control case: a fresh local lease with a live PID stays FreshLocal,
+// so passive reattach (not adoption) is chosen.
+func TestInspectLeaseLiveLocalPIDIsFreshLocal(t *testing.T) {
+	withCheckProcess(t, func(int) ProcessState { return ProcessAlive })
+	ws := t.TempDir()
+	now := time.Now().UTC()
+	writeLeaseAt(t, ws, &Lease{
+		SessionID:       "test",
+		PID:             4242,
+		Hostname:        currentHostname(),
+		LastHeartbeatAt: now,
+		StartedAt:       now,
+	})
+	if got := InspectLease(ws); got != LeaseStateFreshLocal {
+		t.Errorf("live-PID local lease: InspectLease = %v, want LeaseStateFreshLocal", got)
+	}
+}

internal/session/lease.go

@@ -189,7 +189,7 @@ func CleanupStaleLease(path string, staleAfter time.Duration) (*Lease, error) {
 		}
 		return nil, nil
 	}
-	if IsFresh(&l, time.Now(), staleAfter) {
+	if !IsStale(&l, time.Now(), staleAfter) {
 		return nil, nil
 	}
 	if rmErr := os.Remove(path); rmErr != nil && !errors.Is(rmErr, os.ErrNotExist) {

internal/session/lease_inspect.go

@@ -56,7 +56,7 @@ func InspectLease(wsDir string) LeaseState {
 	if l == nil {
 		return LeaseStateNone
 	}
-	if !IsFresh(l, time.Now(), StaleLeaseAfter) {
+	if IsStale(l, time.Now(), StaleLeaseAfter) {
 		return LeaseStateStale
 	}
 	if l.Hostname != currentHostname() {

internal/session/run_preflight.go

@@ -101,7 +101,7 @@ func runActiveLeaseCheck(opts PreflightOpts) (bool, bool, error) {
 	existing, err := ReadLease(leasePath)
 	switch {
 	case err == nil && existing != nil:
-		if IsFresh(existing, time.Now(), StaleLeaseAfter) {
+		if !IsStale(existing, time.Now(), StaleLeaseAfter) {
 			if opts.Force {
 				return true, true, nil
 			}

internal/session/status.go

@@ -74,7 +74,7 @@ func statusAt(wsDir string, now time.Time) Status {
 	}
 
 	state := SessionStateStale
-	if IsFresh(&l, now, StaleLeaseAfter) {
+	if !IsStale(&l, now, StaleLeaseAfter) {
 		state = SessionStateActive
 	}