refactor(aipass): subprocess to drone @spawn sync-registry — kill last cross-branch engine import (TDPLAN-0006 P3)

init_flow.py:896 was the one place aipass imported spawn's Python directly:
  from aipass.spawn.apps.modules.sync_registry import sync_registry
Replaced with subprocess.run(['drone','@spawn','sync-registry','--fix']) — the
command spawn already exposes — matching the aipass init agent -> drone @spawn
create pattern. Graceful degradation preserved: FileNotFoundError (no drone),
non-zero exit, and timeout are all silently skipped so a registry-sync hiccup
never hard-fails an init update. Safe because init update runs on an existing
project where drone is installed (NOT the pre-drone fresh-init path).

aipass branch now has ZERO direct imports of another branch's ENGINE code.
Remaining cross-branch imports are shared SERVICE layers only (cli Rich UI,
prax logger used in 347 files, trigger events) — infrastructure, not duplication.

Verified: zero aipass.spawn imports in .py code; fresh aipass init still
scaffolds (bootstrap pre-drone intact, 69 tests); 438 tests green (4 new for
the subprocess path: success/failure/missing-drone/timeout); seedgo 100%.

TDPLAN-0006 P3. P4 (.recovery relocate) is the last phase.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -12,6 +12,17 @@ and this project uses [Calendar Versioning](https://calver.org/) in the format
 
 ### Changed
 
+- **No more cross-branch engine imports — `aipass init update` calls spawn via
+  subprocess (TDPLAN-0006 P3).** `init_flow.py` previously did
+  `from aipass.spawn.apps.modules.sync_registry import sync_registry` — the one
+  place aipass reached directly into spawn's Python. Replaced with a subprocess
+  call to the already-existing `drone @spawn sync-registry --fix` (same pattern as
+  `aipass init agent` → `drone @spawn create`), preserving graceful degradation
+  (a missing `drone`, non-zero exit, or timeout is silently skipped — registry
+  sync never hard-fails an update). The aipass branch now has **zero** direct
+  imports of another branch's engine code; the remaining cross-branch imports are
+  shared service layers only (cli Rich UI, prax logging, trigger events). (438
+  tests, seedgo 100%.)
 - **`aipass.common` shared library — dedup spawn/aipass scaffold machinery
   (TDPLAN-0006 P2).** `@spawn` and `@aipass` each carried their own copy of the
   JSON merge/handler utilities and registry discovery. Extracted them into a new

src/aipass/aipass/apps/modules/init_flow.py

@@ -893,12 +893,14 @@ def _handle_init_update(args: list[str]) -> int:
             console.print(f"  ({len(current)} already up to date)")
         # Heal registry: prune stale entries (e.g. cross-project ../paths)
         try:
-            from aipass.spawn.apps.modules.sync_registry import sync_registry
-
-            sync_result = sync_registry(fix=True)
-            pruned = sync_result.get("stale", [])
-            if pruned:
-                console.print(f"  [green]Registry healed:[/green] removed {len(pruned)} stale entry(ies)")
+            sync_proc = subprocess.run(
+                ["drone", "@spawn", "sync-registry", "--fix"],
+                capture_output=True,
+                text=True,
+                timeout=30,
+            )
+            if sync_proc.returncode == 0:
+                console.print("  [green]Registry synced.[/green]")
         except Exception as sync_exc:
             logger.warning("[init_flow] registry sync during update skipped: %s", sync_exc)
 

src/aipass/aipass/tests/test_init_flow.py

@@ -19,6 +19,7 @@ from aipass.aipass.apps.modules.init_flow import (
     TOTAL_STAGES,
     _get_last_completed_stage,
     _get_setup_progress,
+    _handle_init_update,
     _save_stage,
     handle_command,
     print_help,
@@ -574,3 +575,87 @@ class TestStages:
         assert result == {}
         stored = json.loads(tmp_local_json.read_text())
         assert stored["setup_progress"]["last_completed_stage"] == 12
+
+
+# =============================================================================
+# init_update_registry_sync: subprocess_sync
+# =============================================================================
+
+
+_MOD_UPDATE = "aipass.aipass.apps.modules.init_flow"
+
+
+class TestInitUpdateRegistrySync:
+    """Tests for registry sync subprocess call in _handle_init_update."""
+
+    def test_sync_success_prints_message(self, tmp_path: Path) -> None:
+        """Successful drone sync-registry prints 'Registry synced.'"""
+        mock_result = MagicMock(returncode=0)
+        with (
+            patch(
+                "aipass.aipass.apps.handlers.init.bootstrap.update_project",
+                return_value={"updated_files": [], "already_current": []},
+            ),
+            patch(f"{_MOD_UPDATE}.subprocess.run", return_value=mock_result) as mock_run,
+            patch(f"{_MOD_UPDATE}.console") as mock_console,
+            patch(f"{_MOD_UPDATE}.json_handler"),
+        ):
+            rc = _handle_init_update([str(tmp_path)])
+        assert rc == 0
+        mock_run.assert_called_once_with(
+            ["drone", "@spawn", "sync-registry", "--fix"],
+            capture_output=True,
+            text=True,
+            timeout=30,
+        )
+        sync_calls = [c for c in mock_console.print.call_args_list if "Registry synced" in str(c)]
+        assert len(sync_calls) == 1
+
+    def test_sync_failure_degrades_silently(self, tmp_path: Path) -> None:
+        """Non-zero exit from drone sync-registry is silently skipped."""
+        mock_result = MagicMock(returncode=1)
+        with (
+            patch(
+                "aipass.aipass.apps.handlers.init.bootstrap.update_project",
+                return_value={"updated_files": [], "already_current": []},
+            ),
+            patch(f"{_MOD_UPDATE}.subprocess.run", return_value=mock_result),
+            patch(f"{_MOD_UPDATE}.console") as mock_console,
+            patch(f"{_MOD_UPDATE}.json_handler"),
+        ):
+            rc = _handle_init_update([str(tmp_path)])
+        assert rc == 0
+        sync_calls = [c for c in mock_console.print.call_args_list if "Registry synced" in str(c)]
+        assert len(sync_calls) == 0
+
+    def test_sync_missing_drone_degrades_silently(self, tmp_path: Path) -> None:
+        """FileNotFoundError (no drone binary) degrades gracefully."""
+        with (
+            patch(
+                "aipass.aipass.apps.handlers.init.bootstrap.update_project",
+                return_value={"updated_files": [], "already_current": []},
+            ),
+            patch(f"{_MOD_UPDATE}.subprocess.run", side_effect=FileNotFoundError("drone not found")),
+            patch(f"{_MOD_UPDATE}.console") as mock_console,
+            patch(f"{_MOD_UPDATE}.json_handler"),
+        ):
+            rc = _handle_init_update([str(tmp_path)])
+        assert rc == 0
+        sync_calls = [c for c in mock_console.print.call_args_list if "Registry synced" in str(c)]
+        assert len(sync_calls) == 0
+
+    def test_sync_timeout_degrades_silently(self, tmp_path: Path) -> None:
+        """subprocess.TimeoutExpired degrades gracefully."""
+        import subprocess as _sp
+
+        with (
+            patch(
+                "aipass.aipass.apps.handlers.init.bootstrap.update_project",
+                return_value={"updated_files": [], "already_current": []},
+            ),
+            patch(f"{_MOD_UPDATE}.subprocess.run", side_effect=_sp.TimeoutExpired(cmd="drone", timeout=30)),
+            patch(f"{_MOD_UPDATE}.console"),
+            patch(f"{_MOD_UPDATE}.json_handler"),
+        ):
+            rc = _handle_init_update([str(tmp_path)])
+        assert rc == 0