Document "Flow as Capability" (flow registry entries are routable capabilities)

[dgenio]

Goal

Establish that a ChainWeaver flow is itself a routable capability within the Weaver Stack. This means flows can be discovered, selected, and invoked through the same RoutingDecision → CapabilityToken path as any other tool.

What "Flow as Capability" Means

A flow has:

• capability_id — a stable identifier that can appear in contextweaver's capability registry
• Input/output schema fingerprint metadata — can live as an Extended contract field (per weaver-spec Extended tier)
• Routability — contextweaver can include flows in ChoiceCard sets alongside atomic tools

Acceptance Criteria

• Documentation (e.g., docs/FLOW_AS_CAPABILITY.md) explaining:
  • How a flow is registered as a capability
  • What metadata a flow exposes (capability_id, input schema, output schema)
  • How it integrates with contextweaver routing
• A short example showing the full path:
  1. contextweaver routes → picks a flow as a ChoiceCard selection
  2. agent-kernel issues a CapabilityToken for the flow
  3. ChainWeaver executes the flow via the kernel-backed executor
  4. Result returned as Frame
• Flow registry entries include capability_id and optional schema fingerprint metadata
• Unit test: a flow can be serialized to a SelectableItem compatible with the weaver_contracts schema

Dependencies

• Kernel-backed executor (Add optional agent-kernel execution backend (FlowExecutor via Kernel) #89)

Context

Part of Milestone E0 — Connect + Align Boundaries.