feat: usage tracking + knowledge import script

- usage_tracker.py: daily token/call buckets per user (home/{user}/usage.json)
- Hook into local backend (OpenAI usage field) and Gemini API (usage_metadata)
- Claude/Gemini CLI backends produce no structured token data and are not tracked
- Fix CLAUDE.md stale tool count (27 → 39) and refresh tool list
- scripts/import_knowledge.py: walk markdown dirs, chunk by H2, call local LLM
  for summaries, create AE journal entries with path-derived tags; resumable via
  state file; --dry-run and --limit flags for safe testing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cortex/orchestrator_engine.py

@@ -26,6 +26,8 @@ from google.genai import types
 from config import settings
 from llm_client import complete
 from tools import TOOL_DECLARATIONS, call_tool, get_tools_for_role, CONFIRM_REQUIRED
+import usage_tracker
+from persona import _user
 
 logger = logging.getLogger(__name__)
 
@@ -44,6 +46,25 @@ Keep your summary factual and complete. Include relevant URLs, data, and specifi
 If no tools are needed, return an empty summary."""
 
 
+def _track_gemini_usage(response, model_name: str | None) -> None:
+    meta = getattr(response, "usage_metadata", None)
+    if not meta:
+        return
+    prompt_tokens = getattr(meta, "prompt_token_count", 0) or 0
+    completion_tokens = getattr(meta, "candidates_token_count", 0) or 0
+    if prompt_tokens or completion_tokens:
+        try:
+            asyncio.create_task(usage_tracker.record(
+                username=_user.get(),
+                backend="gemini_api",
+                model_name=model_name or settings.orchestrator_model,
+                prompt_tokens=prompt_tokens,
+                completion_tokens=completion_tokens,
+            ))
+        except Exception:
+            pass
+
+
 @dataclass
 class OrchestrateCheckpoint:
     """Saved execution state for a job paused at a confirmation gate."""
@@ -285,6 +306,7 @@ async def _run_from_contents(
                 system_instruction=_ORCHESTRATOR_SYSTEM,
             ),
         )
+        _track_gemini_usage(response, model_name)
 
         candidate = response.candidates[0]
         parts = candidate.content.parts if candidate.content else []
@@ -348,6 +370,7 @@ async def _run_from_contents(
                     system_instruction=_ORCHESTRATOR_SYSTEM,
                 ),
             )
+            _track_gemini_usage(conf_response, model_name)
             conf_parts = (
                 conf_response.candidates[0].content.parts
                 if conf_response.candidates and conf_response.candidates[0].content