fix(status-enum): add paused to ProjectStatus, validate, fix progress

Drift-audit Group 6 + Group 5 #6 (enum-extension / status drift):

- ProjectStatus gains 'paused' — routes and frontend already treated it as
  first-class, but the enum (the source of truth) omitted it and the error
  strings lied. A future CHECK derived from the enum would have rejected
  existing paused rows.
- create_project/update_project now validate status via ProjectStatus at the
  service layer (canonical gate; notes.status has no DB CHECK), so the MCP
  create/update_project path can't persist a typo'd status. MCP docstrings
  realigned to the 4-value domain; route error strings corrected.
- get_milestone_progress: cancelled tasks are excluded from the percent
  denominator (and now reported in status_counts), so a milestone whose only
  open task was cancelled reaches 100% instead of stalling below it.

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

src/fabledassistant/services/milestones.py

@@ -155,8 +155,13 @@ async def get_milestone_progress(milestone_id: int) -> dict:
             status_counts[status] = count
 
         total = sum(status_counts.values())
+        cancelled = status_counts.get("cancelled", 0)
         completed = status_counts.get("done", 0)
-        pct = round(completed / total * 100, 1) if total > 0 else 0.0
+        # Cancelled tasks are resolved work, not pending — exclude them from the
+        # percent-complete denominator so a milestone whose only open task was
+        # cancelled still reaches 100% (and auto-collapses) instead of stalling.
+        active_total = total - cancelled
+        pct = round(completed / active_total * 100, 1) if active_total > 0 else 0.0
 
         return {
             "total": total,
@@ -166,6 +171,7 @@ async def get_milestone_progress(milestone_id: int) -> dict:
                 "todo": status_counts.get("todo", 0),
                 "in_progress": status_counts.get("in_progress", 0),
                 "done": status_counts.get("done", 0),
+                "cancelled": cancelled,
             },
         }