feat(api): installable accounted-api agent skill + openapi-to-skill generator (#1516)

* feat(api): installable accounted-api agent skill + openapi-to-skill generator

Three layers, per the July/August 2026 agent-skills ecosystem (skills.sh /
npx skills add, as used by Stripe/Cloudflare/Supabase for their APIs):

- skills/openapi-to-skill/: generic, installable skill that turns any
  OpenAPI spec into a consumer-side integration skill, with a portable
  stdlib-only inventory/condenser tool and an output template + quality
  checklist encoding the distill-not-restate methodology.
- skills/accounted-api/: the installable skill for our own API, rendered
  deterministically by scripts/api-skill/generate.ts from the v1 endpoint
  registry + hand-authored overlays (auth, conventions, domain gotchas).
  CI gate: npm run apiskill:check (core-build.yml).
- lib/api/v1/registry.ts: generateOpenApiSpec now emits requestBody (incl.
  multipart binary parts) and path parameters, and the Zod converter learned
  .default()/z.record()/.pipe()/.transform(), so the public spec carries
  request contracts instead of prose-only.

Docs: /docs/api landing + /llms.txt now point agents at the skill install;
corrected the stale test-key description in the landing (test keys read
real data and force dry-run writes; they are not sandbox-company bound).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(skills): escape backslashes in markdown table cells (CodeQL js/incomplete-sanitization)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

app/llms.txt/route.ts

@@ -50,6 +50,7 @@ declarations, ingest SIE files, and subscribe to webhooks for state changes.
 
 ## Resources
 
+- Agent skill (full API surface for coding agents): \`npx skills add erp-mafia/accounted --skill accounted-api\`
 - OpenAPI 3.1 spec: ${base}/api/v1/openapi.json
 - Skills catalogue: ${base}/.well-known/skills/index.json
 - Health check: ${base}/api/v1/health