feat(goals): add domain/repo goal tracking and update_workstream MCP tool

- Migration c5d6e7f8a9b0: domain_goals and repo_goals tables, repo_goal_id FK on workstreams
- DomainGoal: one active per domain (partial unique index), status active/archived/superseded
- RepoGoal: integer priority, status active/paused/completed/archived, optional domain_goal_id link
- WorkstreamUpdate schema and router extended with repo_goal_id and repo_goal_id filter
- 6 new MCP goal tools: create_domain_goal, get_domain_goals, activate_domain_goal, create_repo_goal, get_repo_goals, update_repo_goal
- update_workstream MCP tool: patch any subset of workstream fields (title, description, owner, due_date, repo_goal_id, status)
- get_domain_summary extended with goal_guidance (needs_workplan, alignment_warnings) signals
- Dashboard goals.md page and docs/goals.md reference page
- CLAUDE.md template updated to act on goal_guidance signals at session start
- CUST-WP-0010 workplan for this feature

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/schemas/workstream.py

@@ -16,6 +16,7 @@ class WorkstreamCreate(BaseModel):
     owner: str | None = None
     due_date: date | None = None
     repo_id: uuid.UUID | None = None  # GEMS primary: the owning repository
+    repo_goal_id: uuid.UUID | None = None
 
 
 class WorkstreamUpdate(BaseModel):
@@ -25,6 +26,7 @@ class WorkstreamUpdate(BaseModel):
     owner: str | None = None
     due_date: date | None = None
     repo_id: uuid.UUID | None = None
+    repo_goal_id: uuid.UUID | None = None
 
 
 class WorkstreamRead(BaseModel):
@@ -32,6 +34,7 @@ class WorkstreamRead(BaseModel):
     id: uuid.UUID
     topic_id: uuid.UUID
     repo_id: uuid.UUID | None = None
+    repo_goal_id: uuid.UUID | None = None
     slug: str
     title: str
     description: str | None = None