Declare canonical x402 ownership and remove cross-repo settlement drift

[reprewindai-dev]

Why

x402 behavior is currently implemented or described in multiple places across Veklom: cAPI ADRs, BYOS middleware/router code, CAPPO payment middleware, VCCP demo lease logic, Veklom-ID bindings, and legacy/archived PayAPI surfaces.

docs/ADR-005-X402-ESCROW.md already says cAPI does not own the escrow and that its location in cAPI is only because cAPI currently holds the cross-platform ADR registry. That ownership boundary now needs to be made operational, not just documented.

Required architecture decision

Create/update the cross-platform x402 architecture record so each responsibility has exactly one owner:

• payment challenge/discovery
• payment verification/facilitator integration
• settlement persistence/replay protection
• capability authorization after payment
• execution
• evidence/receipt generation
• external verification endpoint
• pricing manifest/source of truth
• escrow (if/when separately authorized)

For every non-owner repo, define whether its x402 code is:

• adapter/client,
• compatibility layer,
• demo,
• deprecated/archive.

Required cleanup map

At minimum review:

• cAPI/docs/ADR-005-X402-ESCROW.md
• BYOS backend/core/middleware/x402.py
• BYOS backend/apps/api/routers/x402.py
• BYOS archived payapi_compliance.py
• CAPPO cappo_backend/services/x402_payment.py
• VCCP src/server/x402-engine.ts
• Veklom-ID x402 identity bindings

Guardrails

• Do not allow multiple hard-coded pricing manifests to present themselves as authoritative.
• Do not let an archived/demo implementation satisfy production capability discovery.
• Settlement success alone must not be documented as proof of successful capability execution.
• External verification must bind payment + capability/version + governed execution + output/evidence.

Acceptance criteria

• ADR names one canonical owner/source of truth per x402 responsibility.
• Every duplicate implementation has an explicit keep/adapter/archive/remove disposition.
• Runtime docs link to the canonical implementation instead of reproducing divergent flows.
• Cross-repo contract tests cover the public challenge and evidence/receipt schema.
• Follow-up cleanup issues are linked from this issue, including BYOS #173/#174 and VCCP Covenant — the governed connection layer (runtime + premium console) #1.