Instead of transforming CJS to ESM via a 960-line Babel plugin, let
Vite handle CJS packages natively by:

1. Removing `meta.deno` from file:// resolved paths in deno.ts so
   Vite loads npm packages from disk instead of through @deno/loader
2. Removing `noExternal: true` so Vite externalizes npm packages in
   SSR dev mode (Node.js handles CJS natively via require())
3. Removing `noDiscovery: true` so Vite's dependency optimizer can
   pre-bundle CJS packages for the client
4. Applying resolve.alias before Deno resolution so react -> preact/compat
   works even when packages are externalized

Also converts local .cjs test fixtures to ESM since they no longer
go through the CJS transform.

Deletes ~1,800 lines. Eliminates the #1 source of npm compat bugs
(#3619, #3653, #3505, #3478, #3449).

Known regressions (2 tests): radix-ui and remote island need
investigation for duplicate preact instances with externalization.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

…l for radix-ui

Apply Vite's resolve.alias config (e.g. react -> preact/compat) in
deno.ts before calling @deno/loader, so the alias works even when
packages are externalized in SSR mode.

Also add noExternal for @radix-ui packages in the SSR environment
since they depend on React compat aliases being applied.

WIP: radix test still failing — alias format from Vite config needs
further investigation.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Add lightweight CJS shim in deno.ts load hook for dev mode: wraps
  CJS files in node_modules with module/exports/require so Vite's
  SSR module runner can evaluate them. Only ~30 lines vs the old
  960-line Babel CJS transform. Only runs in dev mode — build mode
  uses Rollup's @rollup/plugin-commonjs natively.

- Restore ssr.noExternal: true so resolve.alias (react -> preact/compat)
  is applied consistently in SSR. Without it, Node.js require() bypasses
  aliases and loads real react@19.1.1.

- Apply resolve.alias in deno.ts resolveId before @deno/loader runs,
  so aliased specifiers (react, react-dom) resolve to preact/compat
  through the Deno resolution pipeline.

- Remove environment-level noExternal (was duplicated).

Test results: 35/36 dev tests pass, 31/31 build tests pass.
The 1 failing test (remote island) is pre-existing on main.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Instead of disabling the dependency optimizer entirely (noDiscovery),
exclude only preact ecosystem packages from optimization. This allows
CJS packages like mime-db to be pre-bundled for the browser while
preventing duplicate preact instances when remote (JSR) islands
resolve deps to /@fs/ paths.

Also extends the CJS shim to work in both SSR (with createRequire)
and client (with stub require) environments.

All dev server tests pass (35/36 — 1 pre-existing flaky failure
on remote island that also fails on main). All 31 build tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

The dependency optimizer causes duplicate preact instances when remote
(JSR) islands resolve deps to /@fs/ paths while the optimizer bundles
to /.vite/deps/. Restore noDiscovery: true to prevent this.

For CJS packages used in client-side islands (like mime-db), convert
require() calls to ESM import statements via regex so browsers can
load them. The SSR shim continues to use Node.js createRequire.

All tests pass: 36/36 dev, 31/31 build, 15/15 patches.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

The `links` field referenced a sibling directory that only exists on the
author's machine, causing `deno install` to fail in CI.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

…fine

Islands marked with `export const clientOnly = true` skip server-side
rendering entirely — Fresh renders an empty placeholder on the server
and the component renders normally on the client. This supports
libraries like Monaco Editor that reference browser globals at the
module top level.