#822 Introspect real tool signatures for the visual editor (self-documenting param forms)

The visual editor only had rich param forms for 14 hand-curated tools; the other ~90 fell back to a raw args:[JSON]/kwargs:{JSON} box — cryptic, users can't know the correct arguments (feedback: 'light years behind n8n'). Fix: GET /api/v1/tools now introspects each tool's real Python signature (inspect.signature) + Google-style docstring Args, so EVERY tool exposes named, typed, documented parameters (name, type, required, default, description, select options from Literal[...]). Params map to named kwargs (verified tool_func(ctx,*args,**kwargs) accepts command as kwarg). Frontend ParamForm renders n8n-style: label + required + type badge + description + typed widget + default placeholder. Generic tool-discovery over the engine registry — core-safe.