docs(mcp): instruct agents to drive task lifecycle + log work

Adds a 'keep task state honest' directive to the MCP _INSTRUCTIONS: set
in_progress on start, log progress with add_task_log as you go, set done the
moment work completes (never leave finished work at todo), and write a dated
dev-log note on the project at significant landings. Reinforced in the
update_task status docstring. App-layer + always-loaded, no rule/config needed
— closes the gap where finished work (e.g. a shipped plan) sat open because the
lifecycle was available but never prescribed.

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

src/fabledassistant/mcp/server.py

@@ -38,6 +38,18 @@ Mechanics:
 - For optional integer FKs (project_id, milestone_id, parent_id), use 0 to mean
   "not set".
 
+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).
+- Log progress as you go with add_task_log — at meaningful steps, not saved up
+  for the end.
+- The moment a task's work is complete, set it done. Never leave finished work
+  at todo/in_progress — an out-of-date status makes Scribe misrepresent what's
+  left to do.
+- At a significant landing (a merge, a shipped feature, a finished plan), write
+  a short dated dev-log note on the project (create_note) summarizing what
+  landed, and mark the plan/task done.
+
 Scribe maintains a Rulebook system (Rulebook -> Topic -> Rule). Rules carry
 an actionable statement plus optional Why and How-to-apply context. At the
 start of any session that touches Scribe, call list_always_on_rules() to

src/fabledassistant/mcp/tools/tasks.py

@@ -143,7 +143,9 @@ async def update_task(
         task_id: ID of the task to update.
         title: New title, or omit to leave unchanged.
         body: New markdown body, or omit to leave unchanged.
-        status: New status — one of: todo, in_progress, done, cancelled.
+        status: New status — one of: todo, in_progress, done, cancelled. Drive
+            the lifecycle: set in_progress when you start, done when complete —
+            don't leave finished work at todo.
         priority: New priority — one of: none, low, medium, high.
         project_id: New project. Omit (0) to leave unchanged.
         milestone_id: New milestone. Omit (0) to leave unchanged.