docs(linkedin-studio): reconcile discoverability surfaces + skill naming

Wave 3 / Step 12 of the remediation plan (Phase 1 — usable by a non-author).

Fix the discoverability defects the audit flagged:
- skills/linkedin-studio/SKILL.md (the auto-activating router): self-naming 'the
  LinkedIn thought leadership plugin' -> 'LinkedIn Studio' (v3.0 rename leftover);
  the 'All Agents' table corrected from 14 to the real 19 (added editorial-reviewer,
  voice-scrubber, content-reviewer, language-reviewer, fact-reviewer); the 'All
  Commands' table completed to 26 (added headless-review, pivot, carousel) so it
  routes to newsletter/headless-review/pivot/react.
- commands/onboarding.md: '25 commands' -> '26 commands' (x2); pillar count '3-5
  expertise areas' -> '5 expertise areas' (reconciles onboarding's 3-5 with
  setup.md's '5 core topics' and the CLAUDE.md '5 core expertise areas' rule).
- commands/linkedin.md: router table + numbered option list gain headless-review
  and pivot.

Scope note (operator decision, this session): the plan's Verify grep
'grep -rni "thought leadership" skills/ -> no matches' is broader than the brief's
actual criterion (which targets only the router skill's self-naming). 'thought
leadership' is a plugin-wide DOMAIN term — the '8 Thought Leadership Angles'
framework lives in references/thought-leadership-angles.md and is referenced by ~40
files (glossary, agents, post/video/batch commands). Renaming it only inside skills/
would create cross-file inconsistency; renaming it plugin-wide is a separate
vocabulary migration outside Step 12's discoverability scope. Per operator choice,
the router SELF-NAMING is fixed (brief criterion met) and the 4 remaining skills/
hits (linkedin-content-creation headings + one linkedin-strategy phase cell) are
legitimate domain usage kept consistent with the rest of the tree.

setup.md needed no edit: its pillar number was already '5'; reconciliation was a
one-sided fix in onboarding.

Verify: router no longer says 'thought leadership plugin'; grep -nc 'headless-review'
commands/linkedin.md -> 2; onboarding pillar count '5' matches setup.md; SKILL.md
agent table 19 rows, command table 26 rows; structural lint exit 0 (61 passed).

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

plugins/linkedin-studio/commands/linkedin.md

@@ -79,6 +79,8 @@ Present these options to the user:
 | `/linkedin:carousel` | Create structured multi-slide carousel with visual layout guidance |
 | `/linkedin:video` | Create video scripts with hook, body, CTA, captions, and thumbnail suggestions |
 | `/linkedin:newsletter` | Long-form orchestrator — newsletter editions, essays, series articles (research → draft → fact-check → persona-review → lock → delivery). The single long-form entry point |
+| `/linkedin:headless-review` | Cold adversarial review of a FROZEN long-form draft (argument, language, facts, reader-fit) — run before lock, ideally in a fresh session for max independence |
+| `/linkedin:pivot` | Re-open a long-form edition after a substantive late change so cleared gates (fact-check → editorial → persona → headless) re-run before lock |
 | `/linkedin:batch` | Create a full week of content in one session |
 | `/linkedin:calendar` | View and manage your post scheduling queue + run the publish action (mark a scheduled post as published) |
 
@@ -145,6 +147,8 @@ Use AskUserQuestion to ask:
 20. **Create a video** — Script for talking head, screen recording, or slideshow
 21. **Mark published** — I just published a scheduled post
 22. **Write long-form** — Newsletter edition, essay, or series article (`/linkedin:newsletter`)
+23. **Cold review (headless)** — Independent adversarial re-read of a frozen long-form draft before lock (`/linkedin:headless-review`)
+24. **Pivot a long-form edition** — Re-open cleared gates after a late substantive change (`/linkedin:pivot`)
 
 Based on their answer, guide them to the appropriate command or invoke it directly.