feat(#3653): add review.models.cursor — wire modelArg/modelConfigKey for the cursor reviewer lane (#4160)

* feat(#3653): add review.models.cursor — wire modelArg/modelConfigKey for the cursor reviewer lane

cursor-agent exposes --model (204 selectable models) but the cursor lane
declared modelArg: null / modelConfigKey: null, so review.models.cursor
was rejected as an unknown config key and the #1517 reviewer-instances
escape hatch silently discarded a configured model at modelExpansion.

Wire the lane the same way codex already is: inject {{model}} into args
right after -p, set modelArg to --model, and declare modelConfigKey as
review.models.cursor plus its config schema entry. An unconfigured lane
still invokes byte-identically to today.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* docs(#3653): add changeset for review.models.cursor

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* fix(#3653): update co-change surfaces that assumed cursor has no model key

gsd-test surfaced three surfaces still hardcoding "cursor declares no
modelConfigKey", broken by wiring review.models.cursor:

- tests/reviewer-config-federation.test.cjs: the #3691-narrows-#2797
  invariant test listed cursor among lanes that must own no model key.
- tests/settings-integrations.test.cjs: the #3651 keyless-lane test
  listed cursor as keyless, including a live config-set assertion that
  now correctly succeeds instead of failing (swapped to qwen).
- gsd-core/workflows/settings-integrations.md: the settable-keys
  enumeration and two prose call-outs still named cursor as keyless.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* chore(#3653): acknowledge deliberate growth of settings-integrations.md

settings-integrations.md grew 4 bytes because it now enumerates
review.models.cursor as a settable key alongside the other reviewer
lanes, matching the modelConfigKey wired for cursor in this PR.

Emitted-Drift-Ack-Growth: settings-integrations.md — adds review.models.cursor to the settable-keys enumeration and removes cursor from the two keyless-lane call-outs, matching #3653's modelConfigKey change

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* chore(#3653): fix malformed Emitted-Drift-Ack-Growth trailer

The previous commit's trailer was separated from Co-Authored-By by a
blank line, splitting it into an earlier, non-trailer paragraph — git's
trailer parser only recognizes the last contiguous block. Restating it
here immediately adjacent to Co-Authored-By so both parse as trailers.

Emitted-Drift-Ack-Growth: settings-integrations.md — adds review.models.cursor to the settable-keys enumeration and removes cursor from the two keyless-lane call-outs, matching #3653's modelConfigKey change
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

* docs(#3653): backfill changeset pr number

pr:0 -> pr:4160 now that https://github.com/open-gsd/gsd-core/pull/4160 exists.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

---------

Co-authored-by: sim <sim@local>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

gsd-core/workflows/settings-integrations.md

@@ -163,12 +163,13 @@ namespace — any other slug fails with `Unknown config key`.
 Settable keys (the shipped registry's model-bearing lanes):
 
 `review.models.agy` (Antigravity), `review.models.claude`, `review.models.codex`,
-`review.models.gemini`, `review.models.kimi-code`, `review.models.llama_cpp`,
-`review.models.lm_studio`, `review.models.ollama`, `review.models.opencode`.
+`review.models.cursor`, `review.models.gemini`, `review.models.kimi-code`,
+`review.models.llama_cpp`, `review.models.lm_studio`, `review.models.ollama`,
+`review.models.opencode`.
 
-Reviewer lanes `cursor`, `qwen`, and `coderabbit` declare no `modelConfigKey` —
-there is nothing to configure for them here (whether they should have a
-per-lane model key is a separate question, out of scope for this workflow).
+Reviewer lanes `qwen` and `coderabbit` declare no `modelConfigKey` — there is
+nothing to configure for them here (whether they should have a per-lane model
+key is a separate question, out of scope for this workflow).
 If the user asks for one of those, say exactly that and skip.
 
 ```text
@@ -208,8 +209,8 @@ If it is not one of the settable keys, print:
 
 ```text
 Rejected: review.models.<slug> is not settable — only the reviewer lanes whose
-keys are enumerated above can be configured here. (cursor, qwen, and
-coderabbit have no per-lane model key.)
+keys are enumerated above can be configured here. (qwen and coderabbit have no
+per-lane model key.)
 ```
 
 and re-prompt.