fix(gstack): link spec skill, complete gitignore allowlist (BLK-007)

A gstack submodule bump added `spec` (v1.47) and the iOS device-farm
5-skill set (v1.43) but gstack `./setup` was never re-run, leaving all 6
as source-only — unlinked, invisible to Claude and untouched by
reset/`gstack on`.

  - Link `spec` only, surgically: skills/spec/SKILL.md symlink matching
    gstack setup's per-skill pattern (real dir + absolute SKILL.md link).
    Platform-agnostic, useful planning skill. Added to full + web-full
    profiles (must be in the active `full` profile or `set full` would
    re-disable it).
  - iOS skills deliberately NOT linked: this is a Linux host, and the iOS
    device-farm needs a Mac daemon + Tailscale + physical iOS devices.
    Linking them would add 5 dead skills plus passive token cost.
  - Complete the .gitignore gstack allowlist: add the 12 entries missing
    from it — `spec`, the 5 `ios-*` (so they stay ignored if a future
    setup on a Mac materializes them), and 6 already-parked skills
    (document-generate, landing-report, scrape, setup-gbrain, skillify,
    sync-gbrain). The parked ones matter because `gstack on` moves parked
    skills into skills/, where any allowlist gap becomes untracked git
    noise. Also drop the stale `skills/checkpoint` entry (renamed to
    context-save).

Verified: `profile show full`/`web-full` report spec enabled; the
source-vs-allowlist drift check is now empty; profile.sh still parses.

The gstack submodule pointer bump itself is left uncommitted (separate
pending work).

Memory: BLK-007 -> resolved; LRN-025 (gitignore allowlist must cover all
toggleable skills incl. parked, else enabling one = git noise).

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

.claude/tasks/TODO.md

@@ -10,7 +10,7 @@
 - [x] Doc : SKILL.md argument-hint + exemples + output-policy (Makefile générique suffit)
 - [x] shellcheck propre + tests (help/bad-action/none-error/on/off cycle) — état live restauré exact
 - [x] Investigué "fix" full.profile : PAS un bug — curation par design (BDR-017 caveat). Aucun fix code.
-- [ ] FOLLOW-UP (BLK-007) : 6 skills gstack source (ios-*, spec) unlinkés post-bump → re-run gstack ./setup + reconcilier profils (iOS dans profils web ? probablement non)
+- [x] FOLLOW-UP (BLK-007 résolu) : linké `spec` (symlink chirurgical) + ajouté à full/web-full ; iOS NON linké (Linux, besoin Mac+Tailscale) ; `.gitignore` allowlist gstack complété (12 ajouts + checkpoint stale retiré) → `gstack on` git-clean ; LRN-025 capitalisé
 - [x] Capitalize : BDR-018, LRN-024, BLK-007, EVAL-002, journal 2026-06-02 + backfill index (BDR-017, BLK-005/006)
 
 ## README.md overhaul