feat(tasks): add needs_human intervention flag (CUST-WP-0009)

- Migration b4c5d6e7f8a9: adds needs_human (bool) + intervention_note (text) to tasks
- API: needs_human filter on GET /tasks/; 422 if flagged without note
- 3 MCP tools: flag_for_human, clear_human_flag, list_human_interventions
- Dashboard: interventions.md with amber cards and "Mark done" button
- Policy router + workstream DoD policy (workstream-dod.md)
- Workstream lifecycle docs page + workplan CUST-WP-0010
- CLAUDE.md: add step 4 (run fix-consistency after workplan writes)
- consistency_check.py: promote C-11 unlinked tasks from INFO to WARN

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

migrations/versions/b4c5d6e7f8a9_add_needs_human.py

@@ -0,0 +1,33 @@
+"""Add needs_human flag and intervention_note to tasks
+
+Revision ID: b4c5d6e7f8a9
+Revises: a3b4c5d6e7f8
+Create Date: 2026-03-03 00:00:00.000000
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "b4c5d6e7f8a9"
+down_revision: Union[str, None] = "a3b4c5d6e7f8"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "tasks",
+        sa.Column("needs_human", sa.Boolean(), server_default="false", nullable=False),
+    )
+    op.add_column(
+        "tasks",
+        sa.Column("intervention_note", sa.Text(), nullable=True),
+    )
+    op.create_index("ix_tasks_needs_human", "tasks", ["needs_human"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_tasks_needs_human", table_name="tasks")
+    op.drop_column("tasks", "intervention_note")
+    op.drop_column("tasks", "needs_human")