Tree-sitter WASM backend spike/prototype

[kafkade]

Summary

Spike implementation of TreeSitterRegionProvider as optional accuracy backend per ADR-001.

Goals

• Evaluate WASM bundle size impact
• Test cross-platform loading (Windows + Mac)
• Compare accuracy vs regex for tricky cases (comments in strings, template literals)
• Measure initialization and parsing latency
• Determine if it's worth shipping as an option

Non-Goals (spike only)

• Not production-ready
• Not all languages covered
• Not shipped in the extension by default

Acceptance Criteria

• Working prototype for TypeScript/JavaScript
• Performance comparison report vs regex
• Bundle size impact assessment
• Decision document: ship as option, defer, or abandon

[kafkade]

Semver impact: Major (x.0.0)

Introducing an alternative parsing backend (Tree-sitter WASM) is an architectural shift that could change comment detection behavior across languages and adds a WASM bundle-size dependency. If this becomes the default backend, users may see different region boundaries — that's a breaking change in observable behavior. This warrants a major version bump when it ships as the primary parser.