feat: add agentic video analysis and clarify action results

Report device actions as dispatched and preserve full failure details. Route
Flash through McpActionExecutor and use ToolFailure across helper tools and
agent loops instead of inferring failure from response text.

Require model-provided descriptions for coordinate targets. Keep observed
element metadata separate from those descriptions in safety checks, visual
summaries, history, and frontend labels.

Add Gemini Interactions API video analysis with configurable processing mode,
chunk size, and timeouts. Centralize Google provider capabilities and token
usage normalization, and update google-genai to 2.22.0.

Preserve system instructions on follow-up interactions, replan pending chunks
when falling back to static processing, and reject unanswered native video
and audio segments instead of caching placeholder results. Keep helper-tool
failure status intact through history tools and committee calls.

Validation: 1,762 Python unit tests passed (3 skipped), 40 frontend formatter
tests passed, and the production UI build completed. Ruff lint, formatting,
the quality ratchet, and git diff checks passed.

artemis/agents/checker/checker.py

@@ -44,6 +44,7 @@ from langchain_core.tools import BaseTool, tool
 
 from pydantic import BaseModel, Field, ValidationError
 
+from artemis.core.tool_failure import ToolFailure, is_tool_failure
 from artemis.constants import CHECKER_MAX_ITERATIONS
 from artemis.context import ArtemisContext
 from artemis.data_engine.context_vars import CURRENT_TRACE_ID
@@ -57,6 +58,7 @@ from artemis.tools.tool_wrapper import (
     tool_result_messages,
 )
 from artemis.utils.logger import get_logger
+from artemis.utils.task_tree import format_actions_clean
 from artemis.utils.ocr_api import is_ocr_configured, perform_ocr
 from artemis.utils.ocr_xml_fusion import (
     _crop_image_remove_status_bar,
@@ -204,7 +206,11 @@ def build_probe_argv(kind: str, params: dict[str, Any] | None = None) -> list[st
 
 
 async def _execute_probe(ctx: ArtemisContext, argv: list[str]) -> str:
-    """Executes a validated probe argv over the ADB device channel."""
+    """Executes a validated probe argv over the ADB device channel.
+
+    A failed probe answers with a :class:`ToolFailure` so the tool loop marks
+    the result as an error structurally rather than by its wording.
+    """
     try:
         adb_client = ctx.get_adb_client()
         device = adb_client.device(serial=ctx.device.device_id)
@@ -214,7 +220,7 @@ async def _execute_probe(ctx: ArtemisContext, argv: list[str]) -> str:
             text = text[:_PROBE_OUTPUT_LIMIT] + "\n... [output truncated]"
         return text
     except Exception as e:
-        return f"Error executing probe: {e}"
+        return ToolFailure(f"Error executing probe: {e}")
 
 
 def get_probe_tool(ctx: ArtemisContext) -> BaseTool:
@@ -230,7 +236,7 @@ def get_probe_tool(ctx: ArtemisContext) -> BaseTool:
         try:
             argv = build_probe_argv(kind, params)
         except ValueError as e:
-            return f"Error: {e}"
+            return ToolFailure(f"Error: {e}")
         return await _execute_probe(ctx, argv)
 
     return probe_device
@@ -330,8 +336,11 @@ def _format_history(ctx: ArtemisContext, limit: int = 60) -> str:
         action = s.get("action_taken")
         action_str = ""
         if action and not summary:
+            # The shared renderer keeps the target's provenance visible: a
+            # self-described coordinate target reads "'play button' (self-described)",
+            # an observed index target reads "'Login'" with no marker.
             try:
-                action_str = json.dumps(action, ensure_ascii=False)[:160]
+                action_str = format_actions_clean(action)[:160]
             except Exception:
                 action_str = str(action)[:160]
         lines.append(f"- Step {num} ({rel}): {summary or action_str}".rstrip())
@@ -456,7 +465,7 @@ async def _run_check_loop(
                     tool=tool_to_run, args=args, tool_call_id=tc["id"]
                 )
                 text, _ = split_multimodal_result(result_obj)
-                status = "error" if text.startswith("Error") else "success"
+                status = "error" if is_tool_failure(result_obj) else "success"
             except Exception as e:
                 result_obj = f"Error running tool {tool_name}: {e}"
                 status = "error"