fix(gateway): silence background agent terminal output (#3297)

* fix(gateway): silence flush agent terminal output

quiet_mode=True only suppresses AIAgent init messages.
Tool call output still leaks to the terminal through
_safe_print → _print_fn during session reset/expiry.

Since #2670 injected live memory state into the flush prompt,
the flush agent now reliably calls memory tools — making the
output leak noticeable for the first time.

Set _print_fn to a no-op so the background flush is fully silent.

* test(gateway): add test for flush agent terminal silence + fix dotenv mock

- Add TestFlushAgentSilenced: verifies _print_fn is set to a no-op on
  the flush agent so tool output never leaks to the terminal
- Fix pre-existing test failures: replace patch('run_agent.AIAgent')
  with sys.modules mock to avoid importing run_agent (requires openai)
- Add autouse _mock_dotenv fixture so all tests in this file run
  without the dotenv package installed

* fix(display): route KawaiiSpinner output through print_fn to fully silence flush agent

The previous fix set tmp_agent._print_fn = no-op on the flush agent but
spinner output and quiet-mode cute messages bypassed _print_fn entirely:
- KawaiiSpinner captured sys.stdout at __init__ and wrote directly to it
- quiet-mode tool results used builtin print() instead of _safe_print()

Add optional print_fn parameter to KawaiiSpinner.__init__; _write routes
through it when set. Pass self._print_fn to all spinner construction sites
in run_agent.py and change the quiet-mode cute message print to _safe_print.
The existing gateway fix (tmp_agent._print_fn = lambda) now propagates
correctly through both paths.

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

* fix(gateway): silence hygiene and compression background agents

Two more background AIAgent instances in the gateway were created with
quiet_mode=True but without _print_fn = no-op, causing tool output to
leak to the terminal:
- _hyg_agent (in-turn hygiene memory agent)
- tmp_agent (_compress_context path)

Apply the same _print_fn no-op pattern used for the flush agent.

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

* chore(display): remove unused _last_flush_time from KawaiiSpinner

Attribute was set but never read; upstream already removed it.
Leftover from conflict resolution during rebase onto upstream/main.

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

---------

Co-authored-by: Dilee <uzmpsk.dilekakbas@gmail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

gateway/run.py

@@ -573,6 +573,10 @@ class GatewayRunner:
                 session_id=old_session_id,
                 honcho_session_key=honcho_session_key,
             )
+            # Fully silence the flush agent — quiet_mode only suppresses init
+            # messages; tool call output still leaks to the terminal through
+            # _safe_print → _print_fn.  Set a no-op to prevent that.
+            tmp_agent._print_fn = lambda *a, **kw: None
 
             # Build conversation history from transcript
             msgs = [
@@ -2175,6 +2179,7 @@ class GatewayRunner:
                                     enabled_toolsets=["memory"],
                                     session_id=session_entry.session_id,
                                 )
+                                _hyg_agent._print_fn = lambda *a, **kw: None
 
                                 loop = asyncio.get_event_loop()
                                 _compressed, _ = await loop.run_in_executor(
@@ -3885,6 +3890,7 @@ class GatewayRunner:
                 enabled_toolsets=["memory"],
                 session_id=session_entry.session_id,
             )
+            tmp_agent._print_fn = lambda *a, **kw: None
 
             loop = asyncio.get_event_loop()
             compressed, _ = await loop.run_in_executor(