Two bugs in `app_layout::switch_active_context`'s aftermath that
caused the active Context's working environment to drift after a
switch:

- The saved-command runner spawned subprocesses against the launch
  project root instead of the active Context's `root`. After
  switching into a worktree Context, `cargo build` ran against the
  main checkout. `panels::command_panel::show` now takes both
  `exec_root` and `store_root`; `panel_content::render_commands`
  derives `exec_root` from `project::active(...).root` (with the
  launch root as fallback when no Context is active).
- `LspManager` was anchored to the launch root and never re-anchored
  on switch, so rust-analyzer continued reporting against the wrong
  workspace tree. `context_switch::switch_active_context` now calls
  `LspManager::update_root` and re-emits `did_open` for hydrated
  buffers when the active root changes — same path that
  `restore_session` already drives at startup.

End-to-end coverage in `tests/scenarios/context_switch_isolates_
buffers_and_changes.rs`: two Contexts, A=MainCheckout / B=Worktree,
disjoint buffer sets, in-memory mutation in B, switch round-trip,
asserting buffer counts (1 / 2 / 1 / 2), no rope-bleed from B into
A, and chrome-color stability across the round-trip. Drove through
the same `app_layout::switch_active_context` funnel that
`dashboard_dispatch::dispatch` uses in production. Added Harness
primitives (`active_context_id`, `switch_to_context`,
`active_context_color`, etc.) and pub re-exports to expose the
funnel for the test.

Promoted e2e scenarios to a distinct numbered gate in
`scripts/test.sh --gates` (gate 2/4 of 4) so a scenario failure
surfaces before the broader workspace tests. `/ck-commit` now
delegates to that single gate command instead of inlining the cargo
calls, and adds the previously-missing ratchet step.

Ratchet: `app_layout::CkEditorApp::lcom1` 361 → 341 (side effect of
moving `exec_root` derivation off `self.project_root` in
`render_commands`). Changelog entry in `baseline_CHANGELOG.md`.

@@ -464,0 +547,4 @@
+        });
+        let id = ctx.id;
+        let project = ckeditor::app::project_mut(&mut self.app)
+            .expect("no project open");

@@ -2065,0 +2094,4 @@
+        let main_id = ensure_main_checkout(&mut project).unwrap().unwrap();
+
+        let wt_dir = tmp.path().join(CTX_A_DIR);
+        fs::create_dir_all(&wt_dir).unwrap();