ci: default lane C to flattened presets

Run 33517761842 proved the lanes work on CI and measured the real
unresolved-inherits divergence of upstream builds (leaf-only
--load-settings -> built-in defaults for parent keys; #14718 family):
engine comparisons identical, pipeline at 17% similarity, 126 settings
reverted. Default CI to --cli-presets flat for a clean parity signal
downstream of preset loading; raw stays available as a dispatch input to
measure the inherits behavior deliberately.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XqSEqBGY9RYF96J8aCgxGy

.github/workflows/parity.yml

@@ -28,6 +28,10 @@ on:
         description: "branch whose latest successful build_all artifact to slice with"
         required: false
         default: "main"
+      cli_presets:
+        description: "lane C preset handling: flat = flatten inherits (clean parity), raw = leaf as-is (measures the CLI's unresolved-inherits behavior, expect large divergence on unfixed builds)"
+        required: false
+        default: "flat"
 
 permissions:
   contents: read
@@ -109,6 +113,7 @@ jobs:
           done
           python3 orca-test-repo/parity/run_parity.py \
             --slicer-root "$ORCA_SLICER_ROOT" --bin "$ORCA_BIN" \
+            --cli-presets "${{ github.event.inputs.cli_presets || 'flat' }}" \
             --out "$PWD/parity-out" $fixtures
 
       - name: Publish job summary