Publish, delete and module installs rebuild only what changed

Publishing or deleting a flow now splices that one flow into the running
graph instead of reconnecting every node in the installation, saving a
shared node's source rebuilds the flows using it, and installing modules
rebuilds only the flows holding a node that would not load.

Renaming stays on the full rebuild — it rewrites message references in
every other flow's document — and so does startup, which has no graph to
splice into.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01StpRc2C6au1WJ1EUU7fsfu

backend/fluksio/api/routes/flows.py

@@ -425,7 +425,7 @@ async def publish_flow(
             detail={"message": str(exc), "current_version": exc.current},
         )
     _audit("published", name, user)
-    await controller.reload()
+    await controller.reload_flow(name)
     return _detail(controller, published)
 
 
@@ -475,7 +475,7 @@ async def delete_flow(
     # Its files are gone; its values and queued work would otherwise linger.
     await run_in_threadpool(controller.forget_flow, name)
     await run_in_threadpool(_forget_runs, session, name)
-    await controller.reload()
+    await controller.reload_flow(name)
     return Message(message=f"Deleted flow '{name}'")
 
 
@@ -556,7 +556,7 @@ async def save_node_source(
             controller.store.write_lib_source, ref, source.code
         )
         if changed:
-            await controller.reload()
+            await controller.reload_lib_users(ref)
     else:
         await run_in_threadpool(
             controller.store.write_node_source, name, node_id, source.code, True

backend/fluksio/api/routes/modules.py

@@ -44,6 +44,12 @@ async def apply_modules(
 
     A manifest that does not resolve changes nothing: the venv is left as it
     was and the stored manifest is only written once the install succeeded.
+
+    Only the flows already holding a node that would not load are rebuilt,
+    because those are the ones an install is called to fix. A flow that this
+    install *breaks* — a package taken back out from under it — is still green
+    and fails at call time with the node author's own import error, until
+    something rebuilds it.
     """
     ok, output = await run_in_threadpool(modules.sync, body.requirements)
     if not ok:
@@ -65,5 +71,5 @@ async def apply_modules(
     # packages that were just installed — a node that could not import one is
     # the reason this was called, and it stays red until it is built again.
     pool.respawn_all()
-    await controller.reload()
+    await controller.reload_failed_flows()
     return ApplyResult(ok=True, output=output)