feat: migrate to Agno native HITL tool confirmation flow (#158)

Replace the homebrew regex-based tool extraction and manual dispatch
(tool_executor.py) with Agno's built-in Human-In-The-Loop confirmation:

- Toolkit(requires_confirmation_tools=...) marks dangerous tools
- agent.run() returns RunOutput with status=paused when confirmation needed
- RunRequirement.confirm()/reject() + agent.continue_run() resumes execution

Dashboard and Discord vendor both use the native flow. DuckDuckGo import
isolated so its absence doesn't kill all tools. Test stubs cleaned up
(agno is a real dependency, only truly optional packages stubbed).

1384 tests pass in parallel (~14s).

Co-authored-by: Trip T <trip@local>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/config.py

@@ -29,6 +29,13 @@ class Settings(BaseSettings):
     # Discord bot token — set via DISCORD_TOKEN env var or the /discord/setup endpoint
     discord_token: str = ""
 
+    # ── Discord action confirmation ──────────────────────────────────────────
+    # When True, dangerous tools (shell, write_file, python) require user
+    # confirmation via Discord button before executing.
+    discord_confirm_actions: bool = True
+    # Seconds to wait for user confirmation before auto-rejecting.
+    discord_confirm_timeout: int = 120
+
     # ── AirLLM / backend selection ───────────────────────────────────────────
     # "ollama"  — always use Ollama (default, safe everywhere)
     # "airllm"  — always use AirLLM (requires pip install ".[bigbrain]")