remove vm session feature

Cuts the daemon-managed guest-session machinery (start/list/show/
logs/stop/kill/attach/send). The feature shipped aimed at agent-
orchestration workflows (programmatic stdin piping into a long-lived
guest process) that aren't driving any concrete user today, and the
~2.3K LOC of daemon surface area — attach bridge, FIFO keepalive,
controller registry, sessionstream framing, SQLite persistence — was
locking in an API we'd have to keep through v0.1.0.

Anything session-flavoured that people actually need today can be
done with `vm ssh + tmux` or `vm run -- cmd`.

Deleted:
- internal/cli/commands_vm_session.go
- internal/daemon/{guest_sessions,session_lifecycle,session_attach,session_stream,session_controller}.go
- internal/daemon/session/ (guest-session helpers package)
- internal/sessionstream/ (framing package)
- internal/daemon/guest_sessions_test.go
- internal/store/guest_session_test.go
- GuestSession* types from internal/{api,model}
- Store UpsertGuestSession/GetGuestSession/ListGuestSessionsByVM/DeleteGuestSession + scanner helpers
- guest.session.* RPC dispatch entries
- 5 CLI session tests, 2 completion tests, 2 printer tests

Extracted:
- ShellQuote + FormatStepError lifted to internal/daemon/workspace/util.go
  (only non-session consumer); workspace package now self-contained
- internal/daemon/guest_ssh.go keeps guestSSHClient + dialGuest +
  waitForGuestSSH — still used by workspace prepare/export
- internal/daemon/fake_firecracker_test.go preserves the test helper
  that used to live in guest_sessions_test.go

Store schema: CREATE TABLE guest_sessions and its column migrations
removed. Existing dev DBs keep an orphan table (harmless, pre-v0.1.0).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/cli/completion_test.go

@@ -19,10 +19,7 @@ func stubCompletionSeams(
 	d *deps,
 	pingErr error,
 	names map[string][]string,
-	listErr error,
-	sessions map[string][]string,
-	sessionErr error,
-) {
+	listErr error) {
 	t.Helper()
 
 	d.daemonPing = func(ctx context.Context, socketPath string) (api.PingResult, error) {
@@ -37,12 +34,6 @@ func stubCompletionSeams(
 		}
 		return names[method], nil
 	}
-	d.completionSessionLister = func(ctx context.Context, socketPath, vmIDOrName string) ([]string, error) {
-		if sessionErr != nil {
-			return nil, sessionErr
-		}
-		return sessions[vmIDOrName], nil
-	}
 }
 
 func TestFilterPrefix(t *testing.T) {
@@ -82,7 +73,7 @@ func testCmdWithCtx() *cobra.Command {
 
 func TestCompleteVMNamesHappyPath(t *testing.T) {
 	d := defaultDeps()
-	stubCompletionSeams(t, d, nil, map[string][]string{"vm.list": {"alpha", "beta", "gamma"}}, nil, nil, nil)
+	stubCompletionSeams(t, d, nil, map[string][]string{"vm.list": {"alpha", "beta", "gamma"}}, nil)
 
 	got, directive := d.completeVMNames(testCmdWithCtx(), nil, "")
 	if directive != cobra.ShellCompDirectiveNoFileComp {
@@ -95,7 +86,7 @@ func TestCompleteVMNamesHappyPath(t *testing.T) {
 
 func TestCompleteVMNamesDaemonDown(t *testing.T) {
 	d := defaultDeps()
-	stubCompletionSeams(t, d, errors.New("connection refused"), nil, nil, nil, nil)
+	stubCompletionSeams(t, d, errors.New("connection refused"), nil, nil)
 
 	got, directive := d.completeVMNames(testCmdWithCtx(), nil, "")
 	if len(got) != 0 {
@@ -108,7 +99,7 @@ func TestCompleteVMNamesDaemonDown(t *testing.T) {
 
 func TestCompleteVMNamesRPCError(t *testing.T) {
 	d := defaultDeps()
-	stubCompletionSeams(t, d, nil, nil, errors.New("rpc failed"), nil, nil)
+	stubCompletionSeams(t, d, nil, nil, errors.New("rpc failed"))
 
 	got, _ := d.completeVMNames(testCmdWithCtx(), nil, "")
 	if len(got) != 0 {
@@ -118,7 +109,7 @@ func TestCompleteVMNamesRPCError(t *testing.T) {
 
 func TestCompleteVMNamesExcludesAlreadyEntered(t *testing.T) {
 	d := defaultDeps()
-	stubCompletionSeams(t, d, nil, map[string][]string{"vm.list": {"alpha", "beta", "gamma"}}, nil, nil, nil)
+	stubCompletionSeams(t, d, nil, map[string][]string{"vm.list": {"alpha", "beta", "gamma"}}, nil)
 
 	got, _ := d.completeVMNames(testCmdWithCtx(), []string{"alpha"}, "")
 	want := []string{"beta", "gamma"}
@@ -129,7 +120,7 @@ func TestCompleteVMNamesExcludesAlreadyEntered(t *testing.T) {
 
 func TestCompleteVMNamesPrefixFilter(t *testing.T) {
 	d := defaultDeps()
-	stubCompletionSeams(t, d, nil, map[string][]string{"vm.list": {"alpha", "beta", "alphabet"}}, nil, nil, nil)
+	stubCompletionSeams(t, d, nil, map[string][]string{"vm.list": {"alpha", "beta", "alphabet"}}, nil)
 
 	got, _ := d.completeVMNames(testCmdWithCtx(), nil, "alp")
 	want := []string{"alpha", "alphabet"}
@@ -140,7 +131,7 @@ func TestCompleteVMNamesPrefixFilter(t *testing.T) {
 
 func TestCompleteVMNameOnlyAtPos0(t *testing.T) {
 	d := defaultDeps()
-	stubCompletionSeams(t, d, nil, map[string][]string{"vm.list": {"alpha"}}, nil, nil, nil)
+	stubCompletionSeams(t, d, nil, map[string][]string{"vm.list": {"alpha"}}, nil)
 
 	atPos0, _ := d.completeVMNameOnlyAtPos0(testCmdWithCtx(), nil, "")
 	if len(atPos0) != 1 || atPos0[0] != "alpha" {
@@ -155,7 +146,7 @@ func TestCompleteVMNameOnlyAtPos0(t *testing.T) {
 
 func TestCompleteImageNames(t *testing.T) {
 	d := defaultDeps()
-	stubCompletionSeams(t, d, nil, map[string][]string{"image.list": {"debian-bookworm", "alpine"}}, nil, nil, nil)
+	stubCompletionSeams(t, d, nil, map[string][]string{"image.list": {"debian-bookworm", "alpine"}}, nil)
 
 	got, _ := d.completeImageNames(testCmdWithCtx(), nil, "")
 	if !reflect.DeepEqual(got, []string{"debian-bookworm", "alpine"}) {
@@ -165,7 +156,7 @@ func TestCompleteImageNames(t *testing.T) {
 
 func TestCompleteKernelNames(t *testing.T) {
 	d := defaultDeps()
-	stubCompletionSeams(t, d, nil, map[string][]string{"kernel.list": {"generic-6.12"}}, nil, nil, nil)
+	stubCompletionSeams(t, d, nil, map[string][]string{"kernel.list": {"generic-6.12"}}, nil)
 
 	got, _ := d.completeKernelNames(testCmdWithCtx(), nil, "")
 	if len(got) != 1 || got[0] != "generic-6.12" {
@@ -175,58 +166,10 @@ func TestCompleteKernelNames(t *testing.T) {
 
 func TestCompleteImageNameOnlyAtPos0SilentAfterFirst(t *testing.T) {
 	d := defaultDeps()
-	stubCompletionSeams(t, d, nil, map[string][]string{"image.list": {"alpine"}}, nil, nil, nil)
+	stubCompletionSeams(t, d, nil, map[string][]string{"image.list": {"alpine"}}, nil)
 
 	after, _ := d.completeImageNameOnlyAtPos0(testCmdWithCtx(), []string{"alpine"}, "")
 	if len(after) != 0 {
 		t.Errorf("expected silence at pos 1+, got %v", after)
 	}
 }
-
-func TestCompleteSessionNames(t *testing.T) {
-	d := defaultDeps()
-	stubCompletionSeams(t, d,
-		nil,
-		map[string][]string{"vm.list": {"devbox"}},
-		nil,
-		map[string][]string{"devbox": {"planner", "worker"}},
-		nil,
-	)
-
-	// Position 0 → VMs.
-	vms, _ := d.completeSessionNames(testCmdWithCtx(), nil, "")
-	if len(vms) != 1 || vms[0] != "devbox" {
-		t.Errorf("pos 0: got %v", vms)
-	}
-
-	// Position 1 → sessions scoped to args[0].
-	sessions, _ := d.completeSessionNames(testCmdWithCtx(), []string{"devbox"}, "")
-	if !reflect.DeepEqual(sessions, []string{"planner", "worker"}) {
-		t.Errorf("pos 1: got %v", sessions)
-	}
-
-	// Position 1 with prefix filter.
-	filtered, _ := d.completeSessionNames(testCmdWithCtx(), []string{"devbox"}, "wor")
-	if len(filtered) != 1 || filtered[0] != "worker" {
-		t.Errorf("pos 1 prefix: got %v", filtered)
-	}
-
-	// Position 2+ silent.
-	past, _ := d.completeSessionNames(testCmdWithCtx(), []string{"devbox", "planner"}, "")
-	if len(past) != 0 {
-		t.Errorf("pos 2+: got %v", past)
-	}
-}
-
-func TestCompleteSessionNamesDaemonDown(t *testing.T) {
-	d := defaultDeps()
-	stubCompletionSeams(t, d, errors.New("down"), nil, nil, nil, nil)
-
-	got, directive := d.completeSessionNames(testCmdWithCtx(), []string{"devbox"}, "")
-	if len(got) != 0 {
-		t.Errorf("expected no suggestions when daemon down, got %v", got)
-	}
-	if directive != cobra.ShellCompDirectiveNoFileComp {
-		t.Errorf("directive = %d, want NoFileComp", directive)
-	}
-}