feat(ost): v5.6 C — output-style scanner (CA-OST, count 13→14)

New orchestrated scanner output-style-scanner.mjs — first new family since
SKL. Three findings, each pinned to a CONFIRMED V-row of the steering-model
plan + re-verified against code.claude.com/docs/en/output-styles:

- CA-OST-001 (medium, V10): user/project custom style missing
  keep-coding-instructions:true (default false) → silently strips built-in
  software-engineering instructions when active. Scoped to user/project.
- CA-OST-002 (low, V11): plugin style with force-for-plugin:true overrides the
  user's selected outputStyle. Verifiseringsplikt correction — the plan bullet
  said "project/user style," but force-for-plugin is plugin-styles-only per the
  docs, so the check keys on source==='plugin'.
- CA-OST-003 (medium): settings outputStyle matching no built-in
  (Default/Explanatory/Learning/Proactive, case-insensitive) nor discovered
  custom style → dead config.

Byte-stability — a scanner addition, not a field addition. Growing the
scanners array + scanners_ok cannot be hidden by a field strip, but re-seeding
frozen v5.0.0 (the SKL precedent) would now bake in B2's hotspot triple +
claudeMd drift. So, per the B2 lesson, frozen v5.0.0 snapshots are PRESERVED
and the OST entry is stripped at compare time via new
tests/helpers/strip-added-scanner.mjs (wired into json/raw-backcompat + the
Step 5/6 humanizer tests); only SC-5 default-output is regenerated (additive
OST entry, diff reviewed). OST is fixture-gated (no output styles on
marketplace-medium / hermetic HOME → silent).

Wiring: orchestrator; humanizer (OST→Configuration mistake) + humanizer-data
OST family (title-coupled); scoring (OST→Settings, keeps 10 areas). Suite
1012→1023 (+11). Badges: scanners 14, tests 1023, TRANSLATIONS families 15.
Lore swept: README, CLAUDE.md, scanner-internals, humanizer.md. self-audit A/A.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/snapshots/default-output/scan-orchestrator.json

@@ -568,6 +568,20 @@
           "low": 0,
           "info": 0
         }
+      },
+      {
+        "scanner": "OST",
+        "status": "ok",
+        "files_scanned": 0,
+        "duration_ms": 0,
+        "findings": [],
+        "counts": {
+          "critical": 0,
+          "high": 0,
+          "medium": 0,
+          "low": 0,
+          "info": 0
+        }
       }
     ],
     "aggregate": {
@@ -582,7 +596,7 @@
       "risk_score": 11,
       "risk_band": "Medium",
       "verdict": "PASS",
-      "scanners_ok": 12,
+      "scanners_ok": 13,
       "scanners_error": 0,
       "scanners_skipped": 1
     }