[Refactor] Migrate API layer to Hono + Vercel Edge/Node adapter for long-term monorepo stability

[hotlong]

Background

Current monorepo Vercel deployment (see PR #933 and previous 404 diagnostics) relies on a [...path].ts API catch-all entrypoint and a Node.js serverless handler written in a way compatible with Vercel's conventions. However, due to monorepo structure, workspace dependencies, and Vercel's framework/SPA routing, serverless routing and bundling issues persist.

Motivation for Hono + Vercel Adapter Migration

• Vercel now recommends using @hono/vercel (Edge or Node adapter) for TypeScript frameworks instead of manual catch-all entrypoints.
• A single Hono app entrypoint, compatible with Vercel's adapter bootstrap system, is easier to test locally, more portable, and better aligned with both Edge Functions and monorepo dependency resolution with workspaces.
• Code will be future-proofed for hybrid edge+node routes or incremental migration to Edge (when upstream deps are ready).
• Avoids the routing ambiguity and bundling pitfalls of catch-all handlers with complex monorepo imports.

Acceptance Criteria

• The API entrypoint is restructured into a proper Hono app (not a vestigial Next.js-style [...path].ts).
• Hono is initialized directly at the top-level entry point for API (api/index.ts or similar), not as an exported handler.
• The Hono app is exported and wired up via @hono/vercel Node adapter, e.g.:

  import { Hono } from 'hono';
  import { handle } from '@hono/vercel';
  const app = new Hono();
  // ... route wiring ...
  export default handle(app);

• Internal kernel/plugin/registry initialization is guaranteed before the app handles any request; all service imports are compatible with esbuild/nft bundling.
• Vercel routes are configured to anticipate Hono's routing (i.e. no catch-all raw handler, just native Node/Edge adapter bootstrap).
• Monorepo dependencies imported by the app can be resolved without custom includeFiles hacks in vercel.json.
• Add automated tests to ensure /api/v1/meta and /api/v1/packages return 200 OK after deployment.
• All changes are reflected in CHANGELOG.md (or ROADMAP.md). Related issues updated on each progress.

Additional Notes

• Hono's DX enables hybrid Edge+Node deployment model (future cloud scaling).
• This unlocks easier local/testing/dev experience outside Vercel (e.g. with hono serve).
• All API endpoints (including REST, GraphQL, metadata, and packages) should be exposed via Hono's router.
• Kernel boot, broker wiring, and all async service initialization should be moved to top-level app.ts as needed. Async wiring must be non-blocking or use Hono's native async context patterns.

Related

• [🐛] fix: Vercel 404 on /api/v1/meta and /api/v1/packages — path normalisation, kernel boot resilience, broker-optional metadata #933
• Internal: Vercel monorepo 404 debug / deployment breakdown