refactor: extract KapiService authored artifact metadata helpers

[devkade]

Summary

Child slice of #128. Keep KapiService.buildWorkflowPrompt as the shared renderer wrapper, then extract the remaining service-local authored artifact metadata/header sync helpers if they are still orchestration noise.

Evidence

Current PR branch evidence:

• src/application/kapi-service.ts is still 1357 lines with 106 methods/helpers and 52 lines over 180 chars.
• buildWorkflowPrompt correctly delegates to renderRunContractPrompt; no prompt rewrite is needed after refactor: consolidate Track A RunContract formatting #132.
• The authored artifact metadata/header helpers remain at service top level:
  • AUTHORED_METADATA_ARTIFACTS
  • authoredArtifactMetadataHeader
  • syncAuthoredArtifactMetadata
  • normalizeDecisionReportOrder
• These helpers are formatting/sync policy, not core service orchestration.

Scope

• Extract authored artifact metadata/header sync into a small application helper module.
• Keep KapiService as workflow orchestration, not artifact text-format owner.
• Add or preserve tests for context/interview/decision-report header synchronization and decision-report ordering.

Non-goals

• Do not split all of KapiService in this slice.
• Do not change artifact names, storage layout, or .kapi compatibility.
• Do not change Deep Interview or Autoresearch behavior except through preserved helper movement.

Acceptance criteria

• KapiService delegates authored artifact header generation/sync to an extracted helper.
• Existing artifact sync behavior remains backward-compatible.
• Tests cover metadata header sync and decision-report ordering after extraction.
• npm run check, npm run check:unused, and relevant service tests pass.

Suggested verification

npm test -- test/workflow-service.test.ts test/artifact-*.test.ts
npm run check
npm run check:unused
npm run quality:budgets

Part of #128.

[devkade]

Design decision — 2026-05-15

Kade selected the extraction target for this slice:

• Extract authored artifact metadata/header synchronization into src/application/artifact-metadata-sync.ts.
• Keep KapiService focused on workflow orchestration.
• Preserve artifact names, storage layout, .kapi/.ilchul compatibility decisions, Deep Interview behavior, Autoresearch behavior, and decision-report ordering unless separately scoped.