fix(lanes): removing a lane deletes its record only, never the worktree

A lane's `remove` tore down what the lane pointed at: `git worktree remove
--force`, a branch delete, and a drop of the lane's own database. One
mis-click on a dashboard row cost a whole branch's unpushed code — and the
row is the only thing AgentHub actually owns. `remove` now stops the run and
the stack, clears AgentHub's own runtime bookkeeping under
`LANES_ROOT/.state/lane<slot>/`, and deletes the row. The working tree, its
branch, git's worktree records and the database stay exactly where they are,
for the user to delete by hand when they mean to.

That also fixes #28. Removal used to route through `assertDestroyable`, whose
third check demands the cwd appear in `git worktree list`; a managed lane
whose directory git no longer listed answered `ENOTWORKTREE` ("lane is not
listed as a worktree in …") and could never be dropped from the dashboard at
all. Removal no longer asks git anything, so no preflight blocker stops it,
and the unpushed-commits force-gate now applies to `reset` alone — nothing
`remove` does can discard a commit.

The UI follows: one label for both lane kinds ("Delete lane record"), copy
that says what survives, and no Force checkbox on removal.
`removeWorktree`/`removeLaneData` remain in place as guarded primitives; no
route calls them any more.

client/src/components/lanes/DestructiveLaneModal.tsx

@@ -123,16 +123,15 @@ export function DestructiveLaneModal({
 
   const blocked = blockingReason(preflight);
   // Mirrors the server's gate exactly (server/routes/lanes.js): force is required
-  // for `reset`, and for `remove` only when a real worktree is at risk. Forgetting
-  // an adopted lane risks nothing on disk, so it needs no force even with unpushed
-  // commits. Never offered alongside a hard blocker, where confirming is
+  // for `reset` alone. `remove` forgets the lane's row and deletes nothing on
+  // disk — no worktree, no branch, no database — so there is no unpushed work it
+  // could discard. Never offered alongside a hard blocker, where confirming is
   // impossible anyway.
   const requiresForce =
     !blocked &&
     preflight !== null &&
-    preflight.action !== "purge" &&
-    preflight.blocked.includes("unpushed-commits") &&
-    (preflight.action === "reset" || preflight.kind === "managed");
+    preflight.action === "reset" &&
+    preflight.blocked.includes("unpushed-commits");
   const disabled =
     loading || !preflight || Boolean(error) || Boolean(blocked) || (requiresForce && !force);
   const facts = preflight ? Object.entries(expectFor(preflight)) : [];

client/src/components/lanes/__tests__/DestructiveLaneModal.test.tsx

@@ -135,7 +135,7 @@ describe("DestructiveLaneModal", () => {
         onConfirm={onConfirm}
       />
     );
-    const confirmButton = await screen.findByRole("button", { name: "Remove lane" });
+    const confirmButton = await screen.findByRole("button", { name: "Delete lane record" });
     await waitFor(() => expect(confirmButton).not.toBeDisabled());
     // "adopted" is shown as context, not as a refusal.
     expect(screen.getByText(/Only the dashboard's record of it is dropped/)).toBeInTheDocument();
@@ -167,7 +167,7 @@ describe("DestructiveLaneModal", () => {
         onConfirm={onConfirm}
       />
     );
-    const confirmButton = await screen.findByRole("button", { name: "Remove lane" });
+    const confirmButton = await screen.findByRole("button", { name: "Delete lane record" });
     await waitFor(() => expect(confirmButton).not.toBeDisabled());
     expect(screen.queryByRole("checkbox")).not.toBeInTheDocument();
     fireEvent.click(confirmButton);
@@ -191,7 +191,7 @@ describe("DestructiveLaneModal", () => {
     await waitFor(() => expect(confirmButton).toBeDisabled());
   });
 
-  it("ENABLES remove when the worktree directory is missing — the server takes the prune path", async () => {
+  it("ENABLES remove when the worktree directory is missing — the row goes, git's records stay", async () => {
     preflightMock.mockResolvedValue(
       worktreePreflight({
         action: "remove",
@@ -212,7 +212,7 @@ describe("DestructiveLaneModal", () => {
         onConfirm={onConfirm}
       />
     );
-    const confirmButton = await screen.findByRole("button", { name: "Remove lane" });
+    const confirmButton = await screen.findByRole("button", { name: "Delete lane record" });
     await waitFor(() => expect(confirmButton).not.toBeDisabled());
     expect(screen.getByText(/The lane directory is already gone/)).toBeInTheDocument();
     fireEvent.click(confirmButton);
@@ -238,7 +238,7 @@ describe("DestructiveLaneModal", () => {
     await waitFor(() => expect(confirmButton).toBeDisabled());
   });
 
-  it("ENABLES remove when the worktree directory is unreadable — the server attempts removal and falls back to deregistering it", async () => {
+  it("ENABLES remove when the worktree directory is unreadable — nothing on disk is touched either way", async () => {
     preflightMock.mockResolvedValue(
       worktreePreflight({
         action: "remove",
@@ -259,7 +259,7 @@ describe("DestructiveLaneModal", () => {
         onConfirm={onConfirm}
       />
     );
-    const confirmButton = await screen.findByRole("button", { name: "Remove lane" });
+    const confirmButton = await screen.findByRole("button", { name: "Delete lane record" });
     await waitFor(() => expect(confirmButton).not.toBeDisabled());
     expect(screen.getByText(/cannot be read as a Git worktree/)).toBeInTheDocument();
     fireEvent.click(confirmButton);
@@ -268,23 +268,34 @@ describe("DestructiveLaneModal", () => {
     });
   });
 
-  it("shows the Force checkbox only when the sole blocker is unpushed commits, and ticking it enables confirm", async () => {
+  it("never offers Force for a managed removal with unpushed commits — it deletes the row, not the branch", async () => {
     preflightMock.mockResolvedValue(
-      worktreePreflight({ action: "remove", unpushed: 3, blocked: ["unpushed-commits"] })
+      worktreePreflight({
+        action: "remove",
+        head: "abc0000",
+        dirty: 0,
+        untracked: 0,
+        unpushed: 3,
+        blocked: ["unpushed-commits"],
+      })
     );
+    const onConfirm = vi.fn();
     render(
       <DestructiveLaneModal
         lane={makeLane()}
         action="remove"
         open
         onClose={vi.fn()}
-        onConfirm={vi.fn()}
+        onConfirm={onConfirm}
       />
     );
-    const confirmButton = await screen.findByRole("button", { name: "Remove lane" });
-    await waitFor(() => expect(confirmButton).toBeDisabled());
-    fireEvent.click(screen.getByRole("checkbox"));
-    expect(confirmButton).not.toBeDisabled();
+    const confirmButton = await screen.findByRole("button", { name: "Delete lane record" });
+    await waitFor(() => expect(confirmButton).not.toBeDisabled());
+    expect(screen.queryByRole("checkbox")).not.toBeInTheDocument();
+    fireEvent.click(confirmButton);
+    expect(onConfirm).toHaveBeenCalledWith({
+      expect: { head: "abc0000", dirty: 0, untracked: 0, unpushed: 3 },
+    });
   });
 
   it("a local-only managed lane (no-remote warning, unpushed-commits blocker) is resettable with Force", async () => {
@@ -353,10 +364,10 @@ describe("DestructiveLaneModal", () => {
     });
   });
 
-  it("confirming an unpushed-commits removal with Force ticked sends force:true plus the same expect block", async () => {
+  it("confirming an unpushed-commits RESET with Force ticked sends force:true plus the same expect block", async () => {
     preflightMock.mockResolvedValue(
       worktreePreflight({
-        action: "remove",
+        action: "reset",
         head: "abc0000",
         dirty: 0,
         untracked: 0,
@@ -368,13 +379,13 @@ describe("DestructiveLaneModal", () => {
     render(
       <DestructiveLaneModal
         lane={makeLane()}
-        action="remove"
+        action="reset"
         open
         onClose={vi.fn()}
         onConfirm={onConfirm}
       />
     );
-    const confirmButton = await screen.findByRole("button", { name: "Remove lane" });
+    const confirmButton = await screen.findByRole("button", { name: "Reset worktree" });
     fireEvent.click(screen.getByRole("checkbox"));
     await waitFor(() => expect(confirmButton).not.toBeDisabled());
     fireEvent.click(confirmButton);