docs: CHANGELOG and TODOS for the CEO mode handoff and platform line

CHANGELOG.md

@@ -57,6 +57,7 @@ The first two rows are the ones to care about: a review that read nothing, or fo
 - **Required team mode also blocks Copilot CLI's skill tool.** Re-run `gstack-team-init required` to upgrade the project hook.
 - **`gstack-qa-evidence capture` prints a `revalidate` list after your inputs change**, naming the probes to rerun on current inputs before `materialize`; `materialize` says its verdict is final for that report root, so rerun the listed probes first.
 - **/gstack-upgrade asks you to paste the absolute path Step 2 prints**; every later step checks it is inside gstack's checkout before running git.
+- **/plan-ceo-review prints its mode handoff** by running `gstack-ceo-mode-handoff` right after the mode is chosen (by you or by a saved preference), so the selected mode and approved decisions always appear before the review continues.
 - **Browser setup names the platform when Aside is absent:** the probe prints `NEEDS_ASIDE: <OS>` (was `NEEDS_ASIDE`), and the macOS-only download pitch trusts that line instead of re-checking the OS. `GSTACK_PLATFORM` overrides it for tests and unusual hosts; set it in your shell, never a project `.env`.
 
 ### Security

TODOS.md

@@ -130,6 +130,13 @@ Deferred from the approved severe fix wave (docs/designs/SEVERE_FIX_WAVE_2026_10
   in 4 (36633323521, 36641820398, 36903600510 before this wave; 37176837432),
   auto-decide-preserved red in 5 (36633323521, 36776104571, 36787269090,
   36920606897 before this wave; 37176837432). Effort M.
+  **Completed:** v1.91.19.0 (2026-10-04). Step 0E now runs
+  `gstack-ceo-mode-handoff`, which prints the handoff line as a tool result,
+  and the auto-decide detector accepts the documented line with its
+  `Approved decisions:` suffix (trial 1 printed it and was rejected; the replay
+  is `test/fixtures/auto-decide-handoff-line-e354.json`). Local paid trials after
+  the repair: auto-decide-preserved 1/1, plan-ceo-mode-routing 1/1 (both modes);
+  every session ran the helper.
 - **Floor runner cannot grant an owned Edit when the TTY collapses spaces** —
   PR run 37176835584 (7249f01): plan-ceo-finding-floor timed out at 600 s with
   the native "Do you want to make this edit to gstack-test-plan-ceo-floor.md?"