enhance(#2295): record the resolved model per reviewer in REVIEWS.md frontmatter (#3649)

* test(#2295): failing-first coverage for per-lane resolved-model recording

* feat(#2295): record the resolved model per reviewer lane

* docs(#2295): document the recorded reviewer model and its provenance

* fix(#2295): refuse control characters in a recorded model value

* test(#2295): correct watermark assertions for the widened mark shape

* fix(#2295): anchor the role-manipulation injection pattern at a word boundary

* feat(#2295): record the applied reasoning effort in the model value

* chore(#2295): backfill changeset pr number

* chore(#2295): restore em-dash in changeset body

---------

Co-authored-by: sim <sim@local>

docs/COMMANDS.md

@@ -1614,6 +1614,8 @@ Reviewers reached through `--all` or `review.default_reviewers` behave different
 
 **Produces:** `{phase}-REVIEWS.md` — consumable by `/gsd-plan-phase --reviews`
 
+Its frontmatter records the model each reviewer resolved to, as `models:` (the model id, or `unknown`, with a `(reasoning=<level>)` suffix when GSD applied a reasoning effort to that lane) and `model_sources:` (how each value was determined — `pinned`, `served`, `requested`, `banner`, `transcript`, or `unknown`). See [Resolved model recording](CONFIGURATION.md#resolved-model-recording-2295).
+
 ```bash
 # set project default reviewers for no-flag /gsd-review runs
 gsd config-set review.default_reviewers '["gemini","codex"]'