docs(scribe): true up plugin + MCP docs after calendar/entity removal

Milestone #194 plugin/docs slice.

- plugin.json: "second brain" framing -> "system-of-record"; bump
  0.1.11 -> 0.1.12 (any plugin/ change must bump the manifest, issue #1040)
- plugin/README.md + using-scribe SKILL + scribe_static_context: drop
  events/typed-entities from the surface lists; "second brain" -> "system
  of record" in the SessionStart context Claude reads each session
- docs/api-keys-and-mcp.md: drop the Typed-entities + Events MCP tool rows,
  add the Systems row
- README.md: rewrite the stale front-matter (chat/RAG/calendar/weather/push
  described a pre-pivot product) to the current Claude-driven work store

Deeper pre-pivot doc-rot in docs/features.md + docs/api-reference.md
(chat/journal/weather/web-research) is tracked separately as an issue.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BPtbSzA4JLMAKgFZ8VTg7Q

plugin/README.md

@@ -3,8 +3,8 @@
 Turns a self-hosted [Scribe](https://git.fabledsword.com/bvandeusen/FabledScribe)
 instance into a first-class Claude Code extension:
 
-- **MCP tools** over your notes, tasks, projects, milestones, events, typed
-  entities, and rulebook (the `scribe` server).
+- **MCP tools** over your notes, tasks, projects, milestones, systems, and
+  rulebook (the `scribe` server).
 - **Session-start push channel** — a `SessionStart` hook injects your always-on
   rules + active-project context so Scribe surfaces *without being asked*.
 - **Universal process-skills** — brainstorm, systematic-debugging, TDD,