refactor(lexer): split classify pipeline stage into multiple files

[overlookmotel]

Pure refactor. No code changes, just moving code around.

Split classify pipeline stage into multiple files.

• avx2.rs / generic.rs - SIMD and generic impls.
• common.rs - Code shared between both impls.
• mod.rs - Minimal entry point, chooses which impl to load dependent on target.

Additionally, a few stylistic changes in Oxc "house style":

• Re-order code so it reads top-to-bottom - imports and consts first, then entry points, private fns/helpers lower down.
• Combine imports into a single use statements.
• Line breaks between functions.

The split of SIMD/generic into separate files is the main point. This is a precursor to switching over to runtime feature detection, instead of compile-time.

[overlookmotel]

• refactor(lexer): group coalesce pipeline stage code into directory #26305
• refactor(lexer): split carve pipeline stage into multiple files #26304
• refactor(lexer): split classify pipeline stage into multiple files #26303 👈 (View in Graphite)
• main

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[Copilot]

🟢 Approval recommended

The changes appear to be a straightforward module/file split with preserved call sites and conditional compilation behavior, and I did not find any functional or API-affecting issues within the changed regions.

Pull request overview

Refactors the pipeline::classify stage in oxc_lexer by splitting the previous single-module implementation into multiple files while keeping the same compile-time AVX2 vs generic selection and shared helpers.

Changes:

• Introduces a new pipeline/classify/ module with mod.rs as a minimal entry point that conditionally selects AVX2 or generic classify.
• Moves the AVX2 implementation into avx2.rs and the non-SIMD implementation into generic.rs.
• Extracts shared logic (misc_pre / misc_post and UTF-8 / Unicode whitespace helpers) into common.rs and re-exports it from the classify module.

File summaries

File	Description
crates/oxc_lexer/src/pipeline/classify/mod.rs	New module entry point selecting AVX2 vs generic implementation and re-exporting shared helpers.
crates/oxc_lexer/src/pipeline/classify/avx2.rs	Contains the AVX2/BMI2 SIMD classify implementation moved from the previous monolithic module.
crates/oxc_lexer/src/pipeline/classify/generic.rs	Contains the non-SIMD classify implementation and lookup-table construction moved from the previous monolithic module.
crates/oxc_lexer/src/pipeline/classify/common.rs	Contains shared misc_pre / misc_post logic and helper routines extracted from the previous module.
crates/oxc_lexer/src/pipeline/classify.rs	Removes the old monolithic classify module file after splitting into the new directory-based module.

Review details

• Files reviewed: 5/5 changed files
• Comments generated: 0
• Review effort level: Lite

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[overlookmotel]

This stack marked as draft as expecting a PR from @ShanonJackson which plan to merge first, and then will rebase this on top.