refactor: extract Kanban graph persistence into topical sibling

tests/hermes_cli/test_kanban_decompose_db.py

@@ -1,4 +1,4 @@
-"""Tests for kb.decompose_triage_task — the DB-layer atomic fan-out
+"""Tests for decompose_triage_task — the DB-layer atomic fan-out
 from the triage column. LLM-free by design.
 """
 
@@ -9,6 +9,7 @@ from pathlib import Path
 import pytest
 
 from hermes_cli import kanban_db as kb
+from hermes_cli.kanban_db_graph import decompose_triage_task
 from hermes_cli import kanban_db_connect as kbc
 
 
@@ -43,7 +44,7 @@ def test_decompose_creates_children_and_promotes_root(kanban_home):
         {"title": "build it", "body": "write code", "assignee": "engineer", "parents": [0]},
     ]
     with kbc.connect() as conn:
-        child_ids = kb.decompose_triage_task(
+        child_ids = decompose_triage_task(
             conn,
             tid,
             root_assignee="orchestrator",
@@ -72,7 +73,7 @@ def test_decompose_creates_children_and_promotes_root(kanban_home):
 def test_decompose_records_audit_comment_and_event(kanban_home):
     with kbc.connect() as conn:
         tid = _create_triage(conn)
-        child_ids = kb.decompose_triage_task(
+        child_ids = decompose_triage_task(
             conn,
             tid,
             root_assignee="orch",

tests/hermes_cli/test_kanban_worktree_isolation.py

@@ -22,6 +22,7 @@ from pathlib import Path
 import pytest
 
 from hermes_cli import kanban_db as kb
+from hermes_cli.kanban_db_graph import decompose_triage_task
 from hermes_cli import kanban_db_connect as kbc
 from hermes_cli import kanban_db_workspace as kbw
 
@@ -78,7 +79,7 @@ def test_decompose_worktree_children_get_own_workspace(kanban_home):
         )
         conn.commit()
 
-        child_ids = kb.decompose_triage_task(
+        child_ids = decompose_triage_task(
             conn,
             root,
             root_assignee="orchestrator",