fix(ext/node): encode more chars in url.pathToFileURL() (#33397)
## Summary
- Extends `encodePathChars` in `ext/node/polyfills/url.ts` to
percent-encode `^`, `[`, `]`, `|`, and `~` — characters that WHATWG
URL's pathname setter leaves unencoded but that Node.js's
`pathToFileURL` encodes.
- Fixes handling of the Windows extended-path prefix `\\?\`:
- `\\?\C:\...` strips the prefix and is treated as a regular drive path
(matches Node's `file:///C:/...` instead of ending up with `?` as the
hostname).
- `\\?\UNC\server\share\...` is now recognized as an extended UNC path;
hostname is parsed from after the `\\?\UNC\` prefix.
- Rewrites regular UNC parsing to use `indexOf` on the host-end
backslash instead of `split("\\\\")`, which is both faster and correctly
rejects empty-hostname inputs.
- Enables `parallel/test-url-pathtofileurl.js` in the node_compat suite.
## Test plan
- [x] `cargo test --test node_compat -- test-url-pathtofileurl` passes
- [x] Previously-enabled URL tests in the node_compat suite still pass
(`test-url-domain-ascii-unicode`, `test-url-fileurltopath`,
`test-url-format-invalid-input`, `test-url-format-whatwg`,
`test-url-format`, `test-url-parse-format`, `test-url-parse-query`,
`test-url-relative`, `test-url-urltooptions`)
- [x] `deno lint` and `deno fmt --check` pass on the modified file
---------
Co-authored-by: Nathan Whitaker <nathan@deno.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
