Define QFlow replay contract and smoke-test interface

[sehkone]

Problem

The pipeline ends at Validator, but the next consumer is QFlow Replay. Without a defined input contract, there is no way to verify that generated bundles are actually usable downstream.

Scope

• Document the input contract: which bundle files QFlow Replay reads, expected formats, required metadata
• List required and optional files for replay
• Define one smoke-test path: minimum bundle content that QFlow can ingest and produce a result
• Identify any bundle format gaps that would block replay

Out of Scope

• QFlow Replay implementation changes
• Full integration testing with QFlow
• Performance requirements for replay

Done when

• The input contract from bundle to replay is documented
• Required files and formats are listed explicitly
• One smoke-test scenario is defined with expected QFlow behavior
• Any bundle format gaps are filed as follow-up issues

Dependencies

• Freeze v1 contracts across Scenario, Bundle, Ground Truth, and Validator #9 (v1 contract freeze, so bundle format is stable)