fix(linkedin-studio): S1 hardening — method calibration (quick) + Start journey

Hardening phase S1. Tightened the hook character bound from one-sided
(under 140) to the full canonical 110-140 band across the Start-journey
creation surfaces, matching hooks/prompts/content-quality-gate.md:
- quick.md: hook band on Step 2 + Step 5 checklist; added a buzzword check
  and a 150-500 length-band check; checklist tally 6 -> 7.
- onboarding.md: hook band in Phase 3.2 + 3.3 (length + no-links already present).
- first-post.md: hook band in Step 4 + Step 5 (length + no-links already present).
- setup.md: zero-edit pass (all four axes already satisfied).

Adds docs/hardening/log.md (per-command audit trail, 5-step method) and
docs/hardening/review.md (cold /trekreview: ALLOW, 0 BLOCKER/0 MAJOR/1 MINOR).
Lint Failed:0, counts 29/19/25/6 unchanged. No structural/version churn.

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

plugins/linkedin-studio/commands/first-post.md

@@ -98,7 +98,7 @@ Then ask: "Give me a sentence or two about what you have in mind."
 
 Use the 3-line formula (from `/linkedin:quick`):
 
-**Line 1: Hook (under 140 characters)**
+**Line 1: Hook (110-140 characters)**
 - Make it specific to your experience
 - Avoid generic openings
 
@@ -122,7 +122,7 @@ Use the 3-line formula (from `/linkedin:quick`):
 ## Step 5: Simplified Quality Check
 
 For a first post, only check these 4 things:
-- [ ] Hook works in 140 chars?
+- [ ] Hook in the 110-140 band (not just under 140)?
 - [ ] ONE clear point (not three)?
 - [ ] Ends with a question or invitation?
 - [ ] Sounds like YOU (not corporate/AI)?