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>

scanners/lib/humanizer-data.mjs

@@ -820,4 +820,34 @@ export const TRANSLATIONS = {
       recommendation: 'See the details for which skill to trim or turn off.',
     },
   },
+
+  // ─────────────────────────────────────────────────────────────
+  // OST — Output-Style Validation
+  // Category: Configuration mistake
+  // ─────────────────────────────────────────────────────────────
+  OST: {
+    static: {
+      'Custom output style removes built-in coding instructions': {
+        title: 'A custom output style turns off Claude\'s coding know-how',
+        description: 'This style replaces Claude Code\'s built-in coding guidance with only your own text, so while it\'s active Claude forgets how to scope changes, comment, and verify work. The setting that keeps that guidance is off by default.',
+        recommendation: 'Add `keep-coding-instructions: true` to the top of the style file to keep that guidance. If you meant to drop it for a non-coding style, leave it as is.',
+      },
+      'Plugin output style overrides your selected output style': {
+        title: 'A plugin is forcing its own output style on you',
+        description: 'This plugin applies its own output style automatically whenever it\'s on, replacing the one you picked. If two plugins both do this, the first one to load wins.',
+        recommendation: 'If you didn\'t want this, turn off the plugin or remove the force setting from its style. Otherwise there\'s nothing to do — the plugin works this way on purpose.',
+      },
+      'Configured output style does not exist': {
+        title: 'Your chosen output style can\'t be found',
+        description: 'Your settings point to an output style that doesn\'t exist by that name, so Claude Code quietly uses the default instead. The style you wanted never takes effect.',
+        recommendation: 'Check the spelling against your styles (built-ins are Default, Explanatory, Learning, Proactive), add the missing style file, or remove the setting.',
+      },
+    },
+    patterns: [],
+    _default: {
+      title: 'Something about your output styles needs a look',
+      description: 'A check on your output styles flagged something worth reviewing.',
+      recommendation: 'See the details for which output style to adjust.',
+    },
+  },
 };

scanners/lib/humanizer.mjs

@@ -41,6 +41,7 @@ const SCANNER_TO_CATEGORY = {
   DIS: 'Dead config',
   GAP: 'Missed opportunity',
   PLH: 'Configuration mistake',
+  OST: 'Configuration mistake',
 };
 
 /**

scanners/lib/scoring.mjs

@@ -168,6 +168,7 @@ const SCANNER_AREA_MAP = {
   SKL: 'Token Efficiency',
   DIS: 'Settings',
   COL: 'Plugin Hygiene',
+  OST: 'Settings',
 };
 
 /**