[launch-core/indexer] Implement Rootflow V0 fixture engine and verifier reports

[FlowmemoryAI]

Objective

Build the indexer/verifier-side Rootflow V0 engine for deterministic local fixtures.

This is an epic-style launch-core issue. It is not complete with only an observation schema. It must produce Rootflow transitions, verifier reports, and Flow Memory output that downstream dashboard work can render.

Required reading

• docs/ROOTFLOW_V0.md
• docs/FLOW_MEMORY_V0.md
• docs/V0_LAUNCH_ACCEPTANCE.md
• docs/DECISIONS/rootflow-v0.md
• contracts/FLOWPULSE_SCHEMA.md

Scope

Allowed folders:

• services/indexer/
• services/verifier/
• fixtures/
• indexer/verifier docs

Forbidden unless explicitly approved:

• production hosted service deployment
• production RPC credentials
• verifier economics
• staking/slashing

Build requirements

• Parse FlowPulse fixtures.
• Derive source observation identity from receipt/log data.
• Produce MemorySignal objects.
• Link MemoryReceipt objects.
• Produce RootflowTransition objects.
• Produce verifier reports with pending, verified, failed, reorged, and unsupported states.
• Export dashboard-readable fixtures.
• Include deterministic checks or tests.

Acceptance evidence

• A local command or script can run the fixture pipeline.
• Output includes observation, MemorySignal, MemoryReceipt, RootflowTransition, verifier report, and AgentMemoryView or dashboard fixture.
• PR summary maps work to docs/V0_LAUNCH_ACCEPTANCE.md rows.