feat(graceful-handoff)!: integrate with STATE.md continuity system (v3.0.0)

BREAKING: replace the NEXT-SESSION artifact + 3 hooks with a STATE.md-centric,
skill-only design. /graceful-handoff now overwrites the nearest STATE.md (with the
mandatory 👉 NESTE block) instead of writing a separate handover file.

- Remove hooks/ entirely: Stop auto-trigger (operator choice), SessionStart loader
  (redundant with global session-start.sh), statusLine hint (dead — user settings win).
- Invert the pipeline: the model writes STATE.md (only it has the context for 👉 NESTE);
  handoff-pipeline.mjs becomes a slim deterministic helper (--plan / --commit / --dry-run).
- Remote-aware policy: STATE.md tracked on private remotes, local-only (gitignored) on
  public/open mirrors. Authoritative signal: git check-ignore STATE.md.
- SKILL.md rewritten as the Session-Slutt ritual; dropped the Sonnet model pin.
- Docs (README, CLAUDE.md, CHANGELOG), plugin.json 2.1.0→3.0.0, .gitignore cleanup.
- Tests rewritten for --plan/--commit; no-`git add -A` regression preserved. 30/30 green.

Release-cut (tag v3.0.0 + catalog ref bump) pending — separate gated action.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019SiKr4c6GAzQH5n6E6f5NA

.gitignore

@@ -4,7 +4,6 @@ STATE.md
 REMEMBER.md
 ROADMAP.md
 TODO.md
-NEXT-SESSION-PROMPT*.local.md
 *.local.md
 *.local.json
 *.local.sh