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>

capabilities/cursor/capability.json

@@ -129,6 +129,7 @@
       "binary": "cursor-agent",
       "args": [
         "-p",
+        "{{model}}",
         "--mode",
         "ask",
         "--trust",
@@ -138,7 +139,7 @@
       ],
       "promptChannel": "argv-file-ref",
       "outputChannel": "stdout",
-      "modelArg": null,
+      "modelArg": "--model",
       "effortChannel": "none"
     },
     "timeoutFloorMs": 900000,
@@ -148,10 +149,15 @@
     "evidenceClass": "source-grounded",
     "requiresBinaries": [],
     "promptBudgetKey": "review.max_prompt_tokens_per_reviewer.cursor",
-    "modelConfigKey": null,
+    "modelConfigKey": "review.models.cursor",
     "handler": null
   },
   "config": {
+    "review.models.cursor": {
+      "type": "string",
+      "default": "",
+      "description": "Model passed to the Cursor reviewer lane."
+    },
     "review.max_prompt_tokens_per_reviewer.cursor": {
       "type": "number",
       "default": -1,