[0froq]

Fixes #564

Problem

defineHandler(middleware..., handler) stored the handler's result in c.res, which finalizes the Hono context. A page builds its own response after the loader or action runs, and Hono dropped that response:

Request	Without middleware	With middleware (main)
GET page	200, page	500 Body has already been used
valid action	200, page with fresh props	204, empty
invalid action	200, page with errors	400, raw issues JSON

The middleware overloads also dropped a withValidator leaf's validator types.

Fix

defineHandler(mw1, mw2, leaf)
  route : mw1 → mw2 → convertReturnValue(leaf)          (unchanged)
  page  : mw1 → mw2 → leaf → render page / re-render     (middleware wraps the final page response)

• defineHandler records its middleware and leaf (internal module runtime/handler-composition.ts, not exported). Nested compositions are flattened.
• executeComposedHandler works like Hono's compose: a middleware Response replaces c.res, the endpoint's Response becomes c.res, middleware can edit c.res after next(), and it returns the final c.res.
• Pages (runLoader / runPageHandler): run the leaf and build the page response inside the chain. Redirects and other Responses from the loader or middleware are returned as before. shared and headDefaults are read at render time, so per-route middleware can set them.
• Actions: a ValidationError from the leaf, or from middleware before the response exists, becomes field errors. One from the loader re-render is not caught.
• Types: one overload defineHandler(...middleware, typedHandler) returns the typed handler unchanged, so withValidator validators and output reach void/routes.
• Plain handlers (no middleware) behave as before.

Tests

packages/void/test/unit/routing-runtime.test.ts runs pages through a real Hono app (every case fails on main or on the first version of this PR):

• loader with middleware renders the page (JSON and HTML)
• action with middleware re-renders with fresh props, or with field errors (JSON and HTML form post)
• middleware headers before/after next() and shared reach the page (GET and action)
• a short-circuit Response keeps edits that outer middleware makes after next()
• ValidationError from action middleware → field errors; from the loader re-render → loader runs once; after the response exists → error
• deferred props stream through loader middleware; etag() tags each page form

Also define-handler.test.ts (route middleware header edits) and route-type-extraction.typecheck.ts (validators and output kept through middleware, including nesting).

Verification

• vp test run packages/void/test/unit: 362 files, 8246 tests passed
• vp run test --base origin/main: all affected tests passed
• vp run --filter ./packages/void typecheck, vp lint, vp fmt: clean

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