feat(mma): Phase 1 — source_tier tagging at emission

- ai_client: add current_tier module var; stamp source_tier on every _append_comms entry
- multi_agent_conductor: set current_tier='Tier 3' around send(), clear in finally
- conductor_tech_lead: set current_tier='Tier 2' around send(), clear in finally
- gui_2: _on_tool_log captures current_tier; _append_tool_log stores dict with source_tier
- tests: 8 new tests covering current_tier, source_tier in comms, tool log dict format

ai_client.py

@@ -89,6 +89,9 @@ comms_log_callback: Callable[[dict[str, Any]], None] | None = None
 # Signature: (script: str, result: str) -> None
 tool_log_callback: Callable[[str, str], None] | None = None
 
+# Set by caller tiers before ai_client.send(); cleared in finally.
+# Safe — ai_client.send() calls are serialized by the MMA engine executor.
+current_tier: str | None = None
 # Increased to allow thorough code exploration before forcing a summary
 MAX_TOOL_ROUNDS: int = 10
 
@@ -134,12 +137,13 @@ COMMS_CLAMP_CHARS: int = 300
 
 def _append_comms(direction: str, kind: str, payload: dict[str, Any]) -> None:
  entry = {
-  "ts":        datetime.datetime.now().strftime("%H:%M:%S"),
-  "direction": direction,
-  "kind":      kind,
-  "provider":  _provider,
-  "model":     _model,
-  "payload":   payload,
+  "ts":          datetime.datetime.now().strftime("%H:%M:%S"),
+  "direction":   direction,
+  "kind":        kind,
+  "provider":    _provider,
+  "model":       _model,
+  "payload":     payload,
+  "source_tier": current_tier,  # set/cleared by caller tiers; None for main-session calls
  }
  _comms_log.append(entry)
  if comms_log_callback is not None: