137 tests covering: module loading, RGBA helper, constants,
renderer lifecycle, optimized buffer operations (clear, fill, draw,
scissor, opacity, resize, compositing), text buffer (append, clear,
reset, defaults, tabs, highlights, memory buffers), text buffer view
(wrapping, selection, viewport, measurement), edit buffer (text ops,
cursor movement, undo/redo, line operations, word boundaries,
coordinate conversion), editor view (viewport, wrapping, selection,
visual cursor, drawing), syntax style (registration, lookup, attribute
combos, bulk styles), links (alloc, resolve, attribute packing),
hit grid, and buffer+view integration drawing.

Threadsafe callbacks (no more TODOs/no-ops):
- setLogCallback: TSFN bridge for log messages from native render thread
- setEventCallback: TSFN bridge for native events (input, resize, etc.)
- streamSetCallback: TSFN bridge for NativeSpanFeed stream notifications
All three properly create/release napi_threadsafe_function, handle
undefined/null to clear callbacks, and use nonblocking queue mode.

Performance APIs for zero-copy buffer access:
- bufferGetCharArrayBuffer/FgArrayBuffer/BgArrayBuffer/AttributesArrayBuffer:
  Return external ArrayBuffers backed by native memory (no copy)
- bufferDrawTextEncoded: Accept pre-encoded Uint8Array to skip
  per-call UTF-8 conversion overhead
- editBufferGetCursorInto/editorViewGetCursorInto/getCursorStateInto:
  Write cursor state into reusable typed arrays (no object allocation)

JS wrapper additions:
- BufferView class: Lazy typed array views over native buffer memory
  with direct cell writes (bypass FFI for bulk updates)
- CursorState class: Reusable cursor reader (zero allocation per read)
- encodeText(): Cached TextEncoder for pre-encoding text

napi.zig additions:
- createThreadsafeFunction/callThreadsafeFunction/releaseThreadsafeFunction
- acquireThreadsafeFunction for multi-thread access
- getTypedArrayInfo for reading typed array data pointers