refactor: unify agent history and harden runtime diagnostics

Preserve user guidance through history compression, stabilize Flash index targets, and retire withdrawn checks without applying stale verdicts.

Improve runtime diagnostics, tool responses, and history rendering. Simplify documentation and comments.

Validation: 2076 tests passed in the full suite; 381 affected tests and 26 frontend tests passed after cleanup. Ruff and the quality ratchet passed.

mcp_server/base.py

@@ -37,7 +37,9 @@ mcp = FastMCP(
         "Use mobile_run_task to launch autonomous UI workflows on connected Android devices or emulators, "
         "mobile_manage_task to check status or steer execution, "
         "mobile_get_device_state to inspect real-time device screen/hierarchy, "
-        "and mobile_inspect_trace to inspect detailed execution steps and visual action overlays."
+        "mobile_inspect_trace to inspect detailed execution steps and visual action overlays, "
+        "and mobile_diagnose whenever a tool errors, no device is found, or the user says "
+        "ARTEMIS is not working: it checks the environment and returns ordered fix steps."
     ),
 )