fix(api): attribute bearer-token actions to the token owner on owner-scoped routes (#4054)

* fix(api): attribute bearer-token actions to the token owner on owner-scoped routes

Owner-scoped chat, session, and upload routes called
get_current_user(), which resolves a bearer ody_ API token to the
sandboxed "api" pseudo-user. A paired API-token client (companion, CLI,
IDE extension) therefore saw and created a separate "api"-owned silo
instead of the owner's data.

effective_user() already exists for exactly this: it attributes a token's
actions to request.state.api_token_owner, is identical to
get_current_user() for cookie sessions, and falls back safely when a
token has no owner. session_routes.py was already migrated; this
completes the migration for the remaining owner-scoped routes:

- chat_helpers.py: chat-privilege enforcement, message attribution, prefs/context
- chat_routes.py: orphaned-endpoint owner, session-auth owner, message search
- upload_routes.py: upload owner attribution + access checks

The /api/models swap is intentionally omitted: #4292 already migrated it
to effective_user (plus the chat-scope gate and ownerless-token 403), so
this PR keeps dev's version of routes/model_routes.py unchanged.

chat_routes.py keeps importing get_current_user for the workspace owner
gate; session_routes.py drops the now-unused import.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* test: target effective_user in auth monkeypatches and owner-scope assertion

The owner-scoped routes now call effective_user() instead of
get_current_user(), so the tests that stubbed get_current_user (or
asserted on it) follow suit:

- test_chat_helpers.py, test_review_regressions.py,
  test_kv_cache_invalidation_2927.py: monkeypatch effective_user
- test_session_endpoint_owner_scope.py: assert the owner-scope guard uses
  effective_user(request)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

routes/chat_helpers.py

@@ -14,7 +14,7 @@ from core.database import Session as DBSession, ModelEndpoint
 from src.llm_core import normalize_model_id
 from src.endpoint_resolver import normalize_base
 from src.context_compactor import maybe_compact, trim_for_context
-from src.auth_helpers import get_current_user
+from src.auth_helpers import effective_user
 from src.prompt_security import untrusted_context_message
 from routes.prefs_routes import _load_for_user as load_prefs_for_user
 
@@ -78,7 +78,7 @@ def _enforce_chat_privileges(request, sess) -> None:
     which means unrestricted allowed_models / zero cap -> no-op for them.
     """
     try:
-        user = get_current_user(request)
+        user = effective_user(request)
     except Exception:
         user = None
     if not user:
@@ -350,7 +350,7 @@ def fire_message_event(request, webhook_manager, session_id: str, sess, message:
             "session_id": session_id, "model": sess.model, "message": message[:2000],
         }))
     from src.event_bus import fire_event
-    user = get_current_user(request)
+    user = effective_user(request)
     fire_event("message_sent", user)
 
 
@@ -577,7 +577,7 @@ async def build_chat_context(
         fire_message_event(request, webhook_manager, session_id, sess, message, compare_mode)
 
     # Resolve user prefs
-    user = get_current_user(request)
+    user = effective_user(request)
     uprefs = load_prefs_for_user(user)
 
     # Memory enabled?