feat: live progress updates during orchestrator tool loop

The thinking bubble now shows real-time status instead of a static spinner:
  ⚡ Round 1 — thinking…
  ⚡ Round 1 — web_search
  ⚡ Round 2 — thinking…
  ⚡ Generating response…

Implementation: async on_progress callback passed from _run_job into both
orchestrators (_run_from_messages / _run_from_contents). Callback writes to
job["progress"] under the jobs lock; poll responses include the field;
app.js displays it in the thinking bubble when present.

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

cortex/orchestrator_engine.py

@@ -120,6 +120,7 @@ async def run(
     max_risk: str | None = None,
     risk_whitelist: list[str] | None = None,
     risk_blacklist: list[str] | None = None,
+    on_progress=None,  # async (str) -> None; called with live status updates
 ) -> OrchestratorResult:
     """
     Run the full orchestration loop for a task.
@@ -183,6 +184,7 @@ async def run(
         starting_round=0,
         gemini_api_key=api_key,
         max_rounds=max_rounds,
+        on_progress=on_progress,
     )
 
     if checkpoint:
@@ -194,6 +196,9 @@ async def run(
             checkpoint=checkpoint,
         )
 
+    if on_progress:
+        await on_progress("Generating response…")
+
     return await _claude_handoff(
         task=task,
         tool_call_log=tool_call_log,
@@ -306,6 +311,7 @@ async def _run_from_contents(
     gemini_api_key: str | None = None,
     tool_list: list[str] | None = None,
     max_rounds: int | None = None,
+    on_progress=None,
 ) -> tuple[str, OrchestrateCheckpoint | None]:
     """
     Run the ReAct loop from the current contents state.
@@ -317,6 +323,8 @@ async def _run_from_contents(
 
     for round_num in range(starting_round, effective_limit):
         logger.info("Orchestrator round %d for task: %.80s", round_num + 1, task)
+        if on_progress:
+            await on_progress(f"Round {round_num + 1} — thinking…")
 
         response = await asyncio.to_thread(
             client.models.generate_content,
@@ -363,6 +371,8 @@ async def _run_from_contents(
                 pending_tools.append({"name": name, "args": args})
                 logger.info("Tool %s blocked — confirmation required", name)
             else:
+                if on_progress:
+                    await on_progress(f"Round {round_num + 1} — {name}")
                 result_str = await _execute_tool(name, args, tool_callables)
                 logger.info("Tool %s → %d chars", name, len(result_str))
                 executed_results.append({"name": name, "args": args, "result": result_str})