fix(router): scope static responses by HTTP method

Problem

A prebuilt Response is documented and typed as an ActionHandler, but bun-router records it in staticResponses: Map<string, Response>. The HTTP method is discarded.

On Bun 1.4.2, the Bun.serve({ static }) table serves a path for every HTTP method. This means:

router.post('/ready', new Response('posted'))

also answers GET /ready, and registering two static responses for the same path lets the later method overwrite the earlier one. The registration also overwrites duplicate method/path entries even though the fetch router uses first registration wins.

The static table is not rebuilt by router.reload(), so prebuilt responses can disappear after reload.

Bun 1.4.2 evidence

A direct Bun probe returned the static response for both GET and POST. A method-scoped native route preserves the intended contract:

routes: {
  '/ready': { POST: new Response('posted') },
}

An absent method falls through to fetch, which lets bun-router retain its existing 404, 405, middleware, and fallback semantics. GET continues to answer HEAD automatically.

Proposed fix

• Retain prebuilt responses by path and HTTP method.
• Merge them into Bun's method-scoped routes table on serve() and reload().
• Merge compatible dynamic native routes into the same table when nativeRoutes: true.
• Preserve first registration wins for each method/path pair.
• Add Bun 1.4.2 HTTP coverage for method isolation, multiple methods on one path, duplicate registration, fetch fallback, and reload.
• Keep prebuilt responses on Bun's zero-allocation path without invoking middleware or request context.

Implemented on main by c3baec0.

The router now retains each prebuilt response by path and HTTP method, merges it into Bun's method-scoped native routes table, preserves first registration, combines static and dynamic native methods, and rebuilds the static table on reload.

Validated with the exact Bun 1.4.2 release:

• full router suite: 570 passed, 0 failed
• TypeScript checks: passed
• package build: passed
• touched-file pickier lint: passed

The new HTTP coverage verifies method isolation, multiple static methods on one path, static/dynamic duplicate order, native route merging, and reload behavior.

Hosted CI is green for c3baec09d48d7ea6f92b26c75f5501fdcb375801: https://github.com/stacksjs/bun-router/actions/runs/35574869684

Lint, type checks, all tests, build, and the commit package publication job passed on the exact pushed commit. Closing as completed.