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>

run_agent.py

@@ -5087,7 +5087,7 @@ class AIAgent:
         spinner = None
         if self.quiet_mode and not self.tool_progress_callback:
             face = random.choice(KawaiiSpinner.KAWAII_WAITING)
-            spinner = KawaiiSpinner(f"{face} ⚡ running {num_tools} tools concurrently", spinner_type='dots')
+            spinner = KawaiiSpinner(f"{face} ⚡ running {num_tools} tools concurrently", spinner_type='dots', print_fn=self._print_fn)
             spinner.start()
 
         try:
@@ -5128,7 +5128,7 @@ class AIAgent:
             # Print cute message per tool
             if self.quiet_mode:
                 cute_msg = _get_cute_tool_message_impl(name, args, tool_duration, result=function_result)
-                print(f"  {cute_msg}")
+                self._safe_print(f"  {cute_msg}")
             elif not self.quiet_mode:
                 if self.verbose_logging:
                     print(f"  ✅ Tool {i+1} completed in {tool_duration:.2f}s")
@@ -5313,7 +5313,7 @@ class AIAgent:
                 spinner = None
                 if self.quiet_mode and not self.tool_progress_callback:
                     face = random.choice(KawaiiSpinner.KAWAII_WAITING)
-                    spinner = KawaiiSpinner(f"{face} {spinner_label}", spinner_type='dots')
+                    spinner = KawaiiSpinner(f"{face} {spinner_label}", spinner_type='dots', print_fn=self._print_fn)
                     spinner.start()
                 self._delegate_spinner = spinner
                 _delegate_result = None
@@ -5343,7 +5343,7 @@ class AIAgent:
                     preview = _build_tool_preview(function_name, function_args) or function_name
                     if len(preview) > 30:
                         preview = preview[:27] + "..."
-                    spinner = KawaiiSpinner(f"{face} {emoji} {preview}", spinner_type='dots')
+                    spinner = KawaiiSpinner(f"{face} {emoji} {preview}", spinner_type='dots', print_fn=self._print_fn)
                     spinner.start()
                 _spinner_result = None
                 try:
@@ -6026,7 +6026,7 @@ class AIAgent:
                     # Raw KawaiiSpinner only when no streaming consumers
                     # (would conflict with streamed token output)
                     spinner_type = random.choice(['brain', 'sparkle', 'pulse', 'moon', 'star'])
-                    thinking_spinner = KawaiiSpinner(f"{face} {verb}...", spinner_type=spinner_type)
+                    thinking_spinner = KawaiiSpinner(f"{face} {verb}...", spinner_type=spinner_type, print_fn=self._print_fn)
                     thinking_spinner.start()
             
             # Log request details if verbose