feat: add iso-2022-jp fatal encoder

[ChALkeR]

Passes on all test data in WPT
But that tests only single-codepoint encode, we need to test more, as iso-2022-jp maintains state
Also need to test failures

[Copilot]

Pull request overview

This PR implements the iso-2022-jp fatal encoder, completing support for all encoding formats in the Web Platform Tests. The encoder uses a state machine to manage transitions between ASCII, Roman, and JIS0208 character sets via escape sequences.

Changes:

• Added iso-2022-jp encoder implementation with state machine logic for character set transitions
• Removed iso-2022-jp exclusions from WPT test loader
• Added preencoder formula for iso-2022-jp pointer-to-bytes conversion

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
tests/wpt/loader.cjs	Removed iso-2022-jp special case exclusions from encoder tests, enabling validation of the new encoder implementation
fallback/multi-byte.js	Added complete iso-2022-jp encoder with state machine (ASCII/Roman/jis0208 states), escape sequence management, halfwidth katakana mapping, and special character handling

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[Copilot]

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[ChALkeR]

This passes basic tests, landing
Will add more tests before the release

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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