context: thread daemon ctx through sessions to agents

Daemon creates a root context, cancelled on SIGTERM. Sessions derive
their context from it. Agent turns derive from session ctx. Tools
get the turn ctx.

Signal propagation:
- SIGTERM → daemonCancel() → all session ctxs cancelled → agent turns exit
- User interrupt → agent.Interrupt() (SIGINT equivalent, turn-level only)
- Session kill → sess.Cancel() → that session's agents stop

Previously sessions used context.Background() — daemon shutdown had
no automatic propagation to running agents.

main.go

@@ -178,7 +178,11 @@ func runServer(sockPath string) {
 	// Elevate broker (initialized after manager; closures capture the pointer).
 	var elevateBroker *elevate.Broker
 
+	daemonCtx, daemonCancel := context.WithCancel(context.Background())
+	defer daemonCancel()
+
 	mgr := mgr.NewManager(mgr.ManagerConfig{
+		Ctx:              daemonCtx,
 		ToolRegistry:     toolRegistry,
 		SkillsRegistry:  skillsRegistry,
 		AgentsDir:        agentsDirs[0],
@@ -332,6 +336,7 @@ func runServer(sockPath string) {
 	<-sigChan
 
 	fmt.Println("shutting down")
+	daemonCancel() // signal all sessions via context propagation
 	if dbusAdapter != nil {
 		dbusAdapter.Close()
 	}

main_test.go

@@ -101,6 +101,7 @@ func newTestSessionManager(t *testing.T) *mgr.Manager {
 	t.Helper()
 	sink := testSink()
 	return mgr.NewManager(mgr.ManagerConfig{
+		Ctx:      context.Background(),
 		Log:      sink.NewLogger("test"),
 		Sink:     sink,
 		ReadFile: func(string) ([]byte, error) { return []byte("#!/bin/sh\n"), nil },
@@ -112,6 +113,7 @@ func newTestSessionManagerWithCore(t *testing.T) *mgr.Manager {
 	t.Helper()
 	sink := testSink()
 	return mgr.NewManager(mgr.ManagerConfig{
+		Ctx:      context.Background(),
 		Log:      sink.NewLogger("test"),
 		Sink:     sink,
 		ReadFile: func(string) ([]byte, error) { return []byte("#!/bin/sh\n"), nil },
@@ -347,6 +349,7 @@ func TestSessionManagerShutdown(t *testing.T) {
 func TestSessionManagerRename(t *testing.T) {
 	sink := testSink()
 	s := mgr.NewManager(mgr.ManagerConfig{
+		Ctx:      context.Background(),
 		Log:      sink.NewLogger("test"),
 		Sink:     sink,
 		ReadFile: func(string) ([]byte, error) { return nil, nil },
@@ -1145,6 +1148,7 @@ func TestSessionManagerCreateSessionEnvExpansion(t *testing.T) {
 	t.Setenv("TEST_CWD", "/expanded/path")
 	sink := testSink()
 	s := mgr.NewManager(mgr.ManagerConfig{
+		Ctx:      context.Background(),
 		Log:      sink.NewLogger("test"),
 		Sink:     sink,
 		ReadFile: func(string) ([]byte, error) { return []byte("#!/bin/sh\n"), nil },
@@ -1169,6 +1173,7 @@ func TestSessionManagerCreateSessionEnvExpansion(t *testing.T) {
 func TestSessionManagerCreateSessionTildeExpansion(t *testing.T) {
 	sink := testSink()
 	s := mgr.NewManager(mgr.ManagerConfig{
+		Ctx:      context.Background(),
 		Log:      sink.NewLogger("test"),
 		Sink:     sink,
 		ReadFile: func(string) ([]byte, error) { return []byte("#!/bin/sh\n"), nil },

mgr/create.go

@@ -137,7 +137,7 @@ func (s *Manager) CreateSession(args []string) (string, error) {
 			// FIXME: Eager dial means session creation blocks on SSH connect.
 			// Eventually make this async or move host info into the prompt
 			// scripts themselves (running remotely via the RPC).
-			rsrv, dialErr := execute.RemoteDial(context.Background(), execute.RemoteConfig{
+			rsrv, dialErr := execute.RemoteDial(s.cfg.Ctx, execute.RemoteConfig{
 				SSHTarget: remoteTarget,
 				CWD:       cwd,
 			})
@@ -228,7 +228,7 @@ func (s *Manager) CreateSession(args []string) (string, error) {
 		})
 	}
 
-	ctx, cancel := context.WithCancel(context.Background())
+	ctx, cancel := context.WithCancel(s.cfg.Ctx)
 	sess := NewSession(sessID, core, ctx, cancel)
 	sessPtr = sess
 	sess.remote = remoteTarget

mgr/manager.go

@@ -28,6 +28,7 @@ func FileMode(name string) (os.FileMode, bool) {
 
 // ManagerConfig holds the dependencies for a Manager.
 type ManagerConfig struct {
+	Ctx         context.Context // daemon context — sessions derive from this
 	AgentsDir   string
 	SessionsDir string
 

mgr/persist.go

@@ -137,7 +137,7 @@ func (s *Manager) restoreSession(ps *agent.PersistedAgent) error {
 	remoteTarget := ps.Remote
 
 	if remoteTarget != "" {
-		rsrv, dialErr := execute.RemoteDial(context.Background(), execute.RemoteConfig{
+		rsrv, dialErr := execute.RemoteDial(s.cfg.Ctx, execute.RemoteConfig{
 			SSHTarget: remoteTarget,
 			CWD:       cwd,
 		})
@@ -237,7 +237,7 @@ func (s *Manager) restoreSession(ps *agent.PersistedAgent) error {
 		},
 	})
 
-	ctx, cancel := context.WithCancel(context.Background())
+	ctx, cancel := context.WithCancel(s.cfg.Ctx)
 	sess := NewSession(sessID, core, ctx, cancel)
 	sessPtr = sess
 	sess.uname = uname