fix(linkedin-studio): ship placeholder voice profile, gitignore real, sentinel detection

Wave 2 / Step 5 of the remediation plan (coupled criticals: voice-leak +
placeholder-detection).

Voice profile (the adopter-default leak):
- Ship a PII-free placeholder at authentic-voice-samples.md carrying a
  <!-- VOICE_PLACEHOLDER --> sentinel + neutral default voice principles.
- Migrate the author's real profile to gitignored authentic-voice-samples.local.md
  (already matched by *.local.md; added an explicit, commented .gitignore entry so
  the intent is unmissable). NO git-history rewrite — the historical file is
  attributed authorship, not a secret (per the plan threat model).
- Add authentic-voice-samples.template.md — a clean fill-in template for adopters.
- personalization-score.mjs: detect the sentinel (deterministic) instead of the
  unreliable `[Your Name]` heuristic, so the placeholder scores 0 voice points and
  a populated profile (sentinel removed) earns the 25.
- Both voice writers replace-not-append on the placeholder: setup.md (merge ->
  replace-if-placeholder) and onboarding.md (append -> replace-if-placeholder), so
  populating removes the sentinel; updated setup.md's stale heuristic table.

Operator decisions (deviations from plan-literal, approved this session):
- KEEP the plugin.json author name. The plan said scrub author -> neutral/org, but
  that contradicts its own LICENSE reasoning (intentional MIT attribution) and all
  5 sibling plugins keep author = the author; scrubbing only this one would create
  inconsistency for zero security gain (the name is public-by-design). The voice
  placeholder fully fixes the adopter-inheritance bug.
- Scrub the stale "January 2026 360Brew" brand from the plugin.json description and
  the "360brew" keyword (locked decision: no publishable model name/date). This is
  a Wave-1 propagation miss surfaced here because plugin.json was in Step 5's
  touch-scope.

Flagged for follow-up (NOT done here — out of Session 2 scope):
- The lint's stat-consistency grep (scripts/test-runner.sh) scans references/,
  commands/, skills/, hooks/prompts/, CLAUDE.md, README.md — but NOT
  .claude-plugin/plugin.json, which is why the 360Brew brand slipped Wave 1.
  Needs a Session-1-scoped lint extension to add plugin.json to the scan set.
- Readers (user-prompt-context.mjs, voice-guardian.md, state-update-reminder.md)
  read the tracked .md (placeholder), per the plan. The operator's real voice now
  lives in the gitignored .local.md, which nothing reads. To use it, readers + the
  voice score should prefer .local.md (matching the user-profile.local.md
  precedent). Deferred as a coherence follow-up for operator review.

Test-first: hooks/scripts/__tests__/personalization-score.test.mjs (red on the
placeholder scoring 25 under the old heuristic, green after the sentinel fix). Hook
suite 62/62, structural lint 0 failed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

plugins/linkedin-studio/commands/onboarding.md

@@ -139,7 +139,13 @@ Use AskUserQuestion:
 4. "Paste a paragraph you've written that sounds like YOU (email, doc, anything)"
 5. "Any words or phrases you'd NEVER use?"
 
-Save responses to `assets/voice-samples/authentic-voice-samples.md` under a new section `## Quick Voice Interview` (append, don't overwrite existing content).
+Save the responses to `assets/voice-samples/authentic-voice-samples.md`. **If the
+file is the shipped placeholder** (it contains `<!-- VOICE_PLACEHOLDER -->`),
+**REPLACE it entirely** with the profile built from the answers — the
+`<!-- VOICE_PLACEHOLDER -->` sentinel must NOT remain, or the voice score stays at
+0 after the user fills it in. **If the file is already a populated profile**, add a
+`## Quick Voice Interview` section instead of overwriting. Either way, the final
+file must contain no `<!-- VOICE_PLACEHOLDER -->`.
 
 **If user profile selected:** Ask for:
 1. Full name

plugins/linkedin-studio/commands/setup.md

@@ -25,7 +25,7 @@ Read these 8 asset files and detect placeholder patterns to calculate the curren
 
 | Category | Weight | File/Directory | Placeholder Detection |
 |----------|--------|----------------|----------------------|
-| Voice samples | 25 | `assets/voice-samples/authentic-voice-samples.md` | Check for `[Your Name]` or if file has <50 lines |
+| Voice samples | 25 | `assets/voice-samples/authentic-voice-samples.md` | Placeholder if it contains the `<!-- VOICE_PLACEHOLDER -->` sentinel (or has <50 lines) |
 | User profile | 20 | `config/user-profile.local.md` | Check if file exists; count `[Your ` placeholders |
 | Case studies | 15 | `assets/case-studies/*.md` | Count non-template `.md` files (exclude `case-study-template.md`) |
 | Frameworks | 10 | `assets/frameworks/*.md` | Count non-template `.md` files (exclude `framework-template.md`) |
@@ -96,14 +96,19 @@ Based on their answer, run the corresponding sub-workflow below.
    - How they handle technical depth
    - How they conclude (CTA style, takeaway style)
 4. Read the existing `assets/voice-samples/authentic-voice-samples.md`
-5. **Merge** new findings with existing content (don't overwrite existing data):
+5. **If the file is the shipped placeholder** (it contains `<!-- VOICE_PLACEHOLDER -->`):
+   **REPLACE it entirely** with the profile built from the user's samples. The
+   placeholder's `<!-- VOICE_PLACEHOLDER -->` sentinel must NOT survive — if it
+   does, the voice category stays at 0 even after the user fills in real data.
+   **Otherwise** (the file is already a populated profile), **merge** new findings
+   into the existing content (don't discard existing data):
    - Update "Core Voice Characteristics" if new patterns found
    - Add new entries to "Do's" and "Don'ts" lists
    - Update "Signature Phrases" with newly detected phrases
    - Add "Vocabulary Preferences" based on word analysis
    - Update "Update Log" with today's date
 
-6. Write the updated file back.
+6. Write the file back, and confirm it contains no `<!-- VOICE_PLACEHOLDER -->`.
 
 **Important:** Ask "Would you like to paste more samples?" after analyzing the first batch. More samples = better voice model.