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

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

docs/FEATURES.md

@@ -1270,6 +1270,12 @@ Each reviewer is a **declared lane**: its binary, prompt and output channels, ti
 - Use `--all` for a full pre-merge sweep without changing project defaults.
 - For local model servers with small context windows, set `review.max_prompt_tokens_per_reviewer` to auto-trim prompts per reviewer — see [Prompt budgets for small-context reviewers](../docs/CONFIGURATION.md#prompt-budgets-for-small-context-reviewers) in CONFIGURATION.md.
 
+**Why record which model produced a review (#2295):** `reviewers:` in the frontmatter recorded which CLIs ran, but not which model each one resolved to. Without a pin, the model is whatever the CLI's own config or internal default happens to pick, so a "Codex vs Antigravity" comparison could quietly be a frontier model against a cheap-tier default with nothing in the record to say so — and a CLI update, or an unrelated config edit, could silently make past and future reviews incomparable.
+
+The fix records the model *and its provenance*. Provenance is what makes the value trustworthy: `pinned` (from `review.models.<slug>`) is certain, while `banner` and `transcript` are recovered from third-party CLI output this project does not own — a startup banner or an undocumented session log.
+
+That third-party dependence is a real trade-off, held honestly rather than papered over: the `banner` and `transcript` arms read formats GSD does not control, so they are best-effort by design and degrade to `unknown` rather than guessing or failing the run. A recorded `unknown` is a real answer — a wrong model name attributed to a review would be worse than none.
+
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 ### 43. Backlog Parking Lot