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

.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "graceful-handoff",
-  "version": "2.1.0",
-  "description": "Auto-trigger session handoff at context-threshold (Stop hook + statusLine hint), with manual /graceful-handoff fallback. Skill-architecture (disable-model-invocation: true) + JSON pipeline + auto-load on session resume.",
+  "version": "3.0.0",
+  "description": "One-command session handoff into the STATE.md continuity system. /graceful-handoff reaches a natural stopping point, overwrites the nearest STATE.md with a complete state-of-play (mandatory '👉 NESTE' block), and commits per remote policy (private → tracked, public mirror → local-only). Skill-only, deterministic STATE helper, no hooks.",
   "author": {
     "name": "Kjell Tore Guttormsen"
   },
@@ -10,11 +10,12 @@
   "keywords": [
     "session",
     "handoff",
+    "state-md",
+    "session-handoff",
     "context-management",
-    "opus-4.7",
+    "continuity",
     "git",
     "workflow",
-    "auto-trigger",
     "skills"
   ]
 }