feat(mcp): make Scribe reflexively recall + scope reads to the active project

The MCP surface advertised writing well but recall poorly, and project
scoping had no anchor that survived past enter_project's snapshot:

- search / list_notes dropped the project_id their services already
  support, so a scoped search was impossible — every query swept all
  projects and bled unrelated work into the session.
- The tool descriptions were mechanical ("Semantic search over the
  user's notes and tasks") with no trigger telling Claude WHEN to reach
  for them; the server instructions were all write-discipline and said
  nothing about searching before answering or starting work.

Changes:
- search, list_notes: add project_id param, wired to the service.
- search, list_notes, list_tasks: trigger-worded descriptions that push
  passing the active project's id and reserve project_id=0 for a
  deliberate cross-project sweep.
- _INSTRUCTIONS: add a 'Reach for Scribe to RECALL, not just to record'
  block — search before answering/starting, check for an existing ticket
  before create_task, scope reads to the active project (which does not
  stick on the server).

Paired with always-on rule #75 in the FabledSword-family rulebook.

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

src/scribe/mcp/server.py

@@ -39,6 +39,22 @@ Mechanics:
   "not set". On update_task, -1 clears an existing FK (e.g. milestone_id=-1
   removes the task from its milestone); 0 leaves it unchanged.
 
+Reach for Scribe to RECALL, not just to record. Scribe is a second brain —
+its value is mostly in what it already holds, so make searching it a reflex,
+not something you wait to be asked for:
+- Before you answer a question about the user's work, or start a task, search
+  Scribe first (search / list_tasks / list_notes). Assume relevant prior art
+  already exists — a related ticket, an earlier decision, a dev-log — and look
+  before you re-derive it or open a duplicate.
+- Before creating a task, search for an existing one (search content_type=
+  'task') — don't open a second ticket for work already tracked.
+- Scope reads to the project in scope. When a project is active (you called
+  enter_project), pass its project_id to search / list_tasks / list_notes so
+  results stay inside that project. Querying with no project_id pulls in every
+  project and bleeds unrelated work into the session — only do it for a
+  deliberate cross-project sweep. The active project does not stick on the
+  server (each call is self-contained); carrying its id forward is on you.
+
 Keep task state honest — this is what makes the project a trustworthy record:
 - When you begin working a task, set it to in_progress (update_task
   status=in_progress).