add cleanup command to remove stale sessions with missing worktrees

src/cli.ts

@@ -4,6 +4,7 @@ import { Command } from "commander"
 import { $} from "bun"
 import { basename, join } from "path"
 import { homedir } from "os"
+import { existsSync } from "fs"
 import { mkdir, symlink, unlink } from "fs/promises"
 import * as git from "./git.ts"
 import * as vm from "./vm.ts"
@@ -598,6 +599,35 @@ program
     process.stdout.write(session.worktree + "\n")
   })
 
+// ── sandlot cleanup ─────────────────────────────────────────────────
+
+program
+  .command("cleanup")
+  .description("Remove stale sessions whose worktrees no longer exist")
+  .action(async () => {
+    const root = await git.repoRoot()
+    const st = await state.load(root)
+    const sessions = Object.values(st.sessions)
+
+    if (sessions.length === 0) {
+      console.log("No sessions to clean up.")
+      return
+    }
+
+    const stale = sessions.filter(s => !existsSync(s.worktree))
+
+    if (stale.length === 0) {
+      console.log("No stale sessions found.")
+      return
+    }
+
+    for (const s of stale) {
+      await state.removeSession(root, s.branch)
+      await unlink(join(root, '.sandlot', s.branch)).catch(() => {})
+      console.log(`✔ Removed stale session: ${s.branch}`)
+    }
+  })
+
 // ── sandlot vm ───────────────────────────────────────────────────────
 
 const vmCmd = program.command("vm").description("Manage the sandlot VM")