feat(plugin): Phase 4 — Scribe Processes auto-surface as local skills

#755 Phase 4. Saved Scribe Processes (DRY pass, Drift Audit, …) now surface as
auto-triggered Claude Code skills instead of pull-only get_process calls.

Design correction vs the plan: stubs live in the USER's ~/.claude/skills/, NOT
plugin/skills/_instance/. The plugin is git-cloned and identical per install, so
instance-specific generated files can't ride in it; personal skills are
live-detected within the session (verified via claude-code-guide). MCP prompts
were the alternative but are pull-only (no relevance auto-surface), so skills are
the right primitive.

- backend: GET /api/plugin/processes manifest (services/plugin_context.
  build_process_manifest) — {name, slug, description} per Process; description is
  the auto-surface trigger (title + preview); slugs deduped, blanks skipped.
- plugin: scribe_sync_processes.sh writes ~/.claude/skills/scribe-proc-<slug>/
  SKILL.md (body = "call get_process(name), follow verbatim") and PRUNES stale
  scribe-proc-* stubs. Fail-open + silent; a transient fetch failure never wipes
  existing stubs. Runs as a 2nd SessionStart hook + via the /scribe:sync command.
- plugin.json 0.1.7 → 0.1.8; README updated.
- tests: build_process_manifest (render, slug dedupe, blank-title skip, preview
  truncation). Sync script's write+prune validated in isolation (plugin/** is not
  CI-covered): correct stubs created, stale pruned, unrelated skills untouched.

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

plugin/README.md

@@ -9,6 +9,10 @@ instance into a first-class Claude Code extension:
   rules + active-project context so Scribe surfaces *without being asked*.
 - **Universal process-skills** — brainstorm, systematic-debugging, TDD,
   writing-plans, verification, receiving-code-review (replaces superpowers).
+- **Your Scribe Processes as skills** — saved Processes are synced into local
+  `~/.claude/skills/scribe-proc-*` stubs that auto-surface by relevance; the
+  stub fetches the live procedure via `get_process`. Refreshed each session and
+  on demand with `/scribe:sync`.
 
 It is designed so you can uninstall `superpowers` and disable auto-memory and
 depend on neither.
@@ -38,6 +42,10 @@ On install you'll be asked for:
   **fail-open**: if Scribe is unreachable it injects nothing and never blocks
   the session.
 - `skills/` → the universal process-skills, surfaced by description match.
+- `hooks/scribe_sync_processes.sh` (a 2nd SessionStart hook) + the `/scribe:sync`
+  command → generate `~/.claude/skills/scribe-proc-*` stubs from your Scribe
+  Processes (via `GET /api/plugin/processes`); also **fail-open**, and pruned to
+  match what exists in Scribe.
 
 ## Notes