Reduce the §3 Capability dataclass from ten fields to five:
id, description, input_schema, output_schema, handler. Removed
fields (name, required_credentials, side_effects,
expected_duration_seconds, cost_estimate) are reintroduced only when a
concrete consumer feature demands them. The v1 invariant is that a
Capability is a typed, named, callable unit and every consumer
(executor, agent tool layer, future HTTP API) sees the same five-field
shape.
Track the initial v2 design document for the SurfSense automation feature.
This is the baseline snapshot of the design before applying the v1-minimum
scope narrowing (capability trimming, MCP deferral, queue-routing deferral).
Subsequent commits trim this down to the v1 scope.
