Make typecheck:apps mandatory in CI

[jithinraj]

Context

v0.10.9 added typecheck:apps as an advisory CI step (continue-on-error: true), mirroring the typecheck:legacy pattern. This provides visibility without blocking release.

Current State

Two apps have pre-existing typecheck errors:

apps/api (3 errors):

• src/index.ts:68 -- Hono c.body() overload mismatch (string vs StatusCode). Fix: use c.json() or cast status.
• src/verifier.ts:7-8 -- @peac/core lacks .d.ts exports. Fix: add types to @peac/core or sunset the import.

apps/bridge (3 errors):

• src/routes/enforce.ts:11, src/routes/readiness.ts:10 -- same @peac/core missing types
• src/routes/readiness.ts:29, src/routes/verify.ts:44 -- @peac/app-api module not found

apps/sandbox-issuer and apps/verifier pass clean.

Fix Strategy

1. @peac/core types: Add types field to @peac/core/package.json pointing to .d.ts output, or add explicit declare module '@peac/core' shims in consuming apps (if sunsetting the package).
2. Hono overload: Replace c.body(JSON.stringify(problem), problem.status) with c.json(problem, problem.status as StatusCode) or use Hono's typed response helpers.
3. @peac/app-api module: Verify bridge still needs this import, fix or remove.
4. Flip CI: Remove continue-on-error: true from typecheck:apps step once all errors resolved.

Acceptance Criteria

• pnpm typecheck:apps passes with zero errors
• CI step is mandatory (no continue-on-error)