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- DomainGoal: one active per domain (partial unique index), status active/archived/superseded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/models/managed_repo.py

@@ -35,6 +35,10 @@ class ManagedRepo(Base, TimestampMixin):
         "Domain", back_populates="repos", lazy="selectin"
     )
 
+    goals: Mapped[list["RepoGoal"]] = relationship(  # noqa: F821
+        "RepoGoal", back_populates="repo", lazy="selectin"
+    )
+
     @property
     def domain_slug(self) -> str:
         return self.domain.slug if self.domain is not None else ""