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- DomainGoal: one active per domain (partial unique index), status active/archived/superseded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

@@ -40,9 +40,16 @@ class Workstream(Base, TimestampMixin):
         nullable=True,
         index=True,
     )
+    repo_goal_id: Mapped[uuid.UUID | None] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("repo_goals.id", ondelete="SET NULL"),
+        nullable=True,
+        index=True,
+    )
 
     topic: Mapped["Topic"] = relationship("Topic", back_populates="workstreams")  # noqa: F821
     repo: Mapped["ManagedRepo"] = relationship("ManagedRepo", lazy="selectin")  # noqa: F821
+    repo_goal: Mapped["RepoGoal"] = relationship("RepoGoal", back_populates="workstreams", lazy="selectin")  # noqa: F821
     tasks: Mapped[list["Task"]] = relationship(  # noqa: F821
         "Task", back_populates="workstream", lazy="selectin"
     )