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>

tests/settings-integrations.test.cjs

@@ -211,7 +211,8 @@ describe('#3651 workflow — review.models settable-set rule', () => {
   test('keyless reviewer lanes have no settable review.models key (#3651)', (t) => {
     // Lanes whose capability declares modelConfigKey: null — the workflow used
     // to walk users into writing these keys, and config-set rejects them.
-    for (const keyless of ['cursor', 'qwen', 'coderabbit']) {
+    // `cursor` gained a real modelConfigKey (#3653) and is no longer keyless.
+    for (const keyless of ['qwen', 'coderabbit']) {
       assert.ok(
         !isValidConfigKey(`review.models.${keyless}`),
         `review.models.${keyless} must not validate (lane declares no modelConfigKey)`
@@ -227,7 +228,7 @@ describe('#3651 workflow — review.models settable-set rule', () => {
     const tmp = createTempProject();
     t.after(() => cleanup(tmp));
     runGsdTools(['config-ensure-section'], tmp);
-    const r = runGsdTools(['config-set', 'review.models.cursor', 'cursor-model'], tmp);
+    const r = runGsdTools(['config-set', 'review.models.qwen', 'qwen-model'], tmp);
     assert.ok(
       !r.success,
       'config-set must reject a keyless lane — the exact error the old workflow steered users into'