Hack Day: FDC3 Hardening + Conformance Regression Pipeline

## Summary
Harden FDC3 integration and add conformance-driven validation to improve interoperability confidence.

## Jump-Off State(s)
- `014-fdc3-intent-interoperability`

## Graph Intent
`canonical candidate`

## Scope
- Expand intent/context handling robustness.
- Add conformance checks and regression harness.
- Improve degraded-mode behavior and diagnostics.

## Acceptance Criteria
- Core TraderX FDC3 flows are deterministic across supported agents.
- Conformance checks run in CI and produce actionable reports.
- Non-agent mode remains fully functional.

## Decision Gate (Promote/Park)
Promote if interop reliability is materially improved and testable.

Begin with the `014-fdc3-intent-interoperability` state and inspect the existing FDC3 intent/context handling and validation paths. Identify the current CI entry point and regression checks before defining conformance coverage. Done means deterministic flows across supported agents, actionable CI reports, and a working non-agent mode.

Written by the indexing model from the issue text.