[Feature] Add PTODSL syntax highlighting support for editors

[Zhendong404]

Summary

Add editor-side syntax highlighting support for PTODSL so PTODSL-authored Python code is easier to read, review, and maintain.

Motivation / use case

PTODSL code uses a Python surface, but it carries a distinct DSL vocabulary such as @pto.jit, @pto.simd, @pto.simt, pto.for_, pto.if_, PTODSL surface types, and scalar.* helpers. Today these files are highlighted as plain Python, which makes PTODSL-specific constructs harder to visually scan in examples, docs, and kernel implementations.

A dedicated highlighting solution would help with:

• faster onboarding for PTODSL users
• clearer code review of PTODSL kernels and examples
• better readability in docs snippets and launch examples
• reduced confusion between ordinary Python control flow and PTODSL device-side control flow

Proposed API / behavior

A good first milestone would be a lightweight VS Code syntax-highlighting package that:

• highlights PTODSL decorators such as @pto.jit, @pto.simd, @pto.simt, and @pto.cube
• highlights PTODSL control-flow helpers such as pto.for_, pto.if_, pto.yield_, and br.then_ / br.else_
• highlights PTODSL surface types and enums under pto.*
• highlights scalar.* helpers
• works both for a dedicated PTODSL language mode and as an injection into ordinary Python files so existing .py PTODSL sources benefit without renaming

The implementation can stay editor-only at first; no PTODSL runtime or compiler behavior needs to change.

Alternatives considered

• Continue using plain Python highlighting only. This is simple, but PTODSL-specific syntax remains visually hidden.
• Build a richer tree-sitter or language-server solution first. This may be valuable later, but a lightweight TextMate-based highlighter is a lower-risk starting point.

Additional context

A draft implementation had been prepared as a PR, but this request is being tracked as an issue first so the feature scope and preferred editor support can be discussed before merging code.