fix(gateway): align content_actions with actual service method names

content_actions.note/dm/say/commit/evidence called write_entry/send/
post_to_channel/git.commit/git.diff(base=)/fetch_branch_for_inspection,
none of which existed on JournalService/A2AService/MessagingService/
GitService/WorkspaceService. Live smoke threw AttributeError on every
content tool. Add the matching gateway-shaped adapters on each service
(scope-string -> JournalEntryType for note; channel-by-slug -> default
group -> active session for say; UUID-or-slug recipient resolution for
dm; branch-name commit + diff(base=) for commit/evidence; project-aware
fetch_branch_for_inspection on workspace). Surfaced live.

tests/unit/gateway/test_content_actions.py

@@ -306,7 +306,7 @@ async def test_dm_with_active_task_succeeds() -> None:
     assert body["task_id"] == str(task_id)
     a2a_svc.send.assert_awaited_once()
     call_kwargs = a2a_svc.send.call_args.kwargs
-    assert call_kwargs["to_agent_slug"] == "be-qa-1"
+    assert call_kwargs["to_agent"] == "be-qa-1"
     assert call_kwargs["skill"] == "code_review"