fix: reduce peak memory ~9× in LZW decoder and TIFF encoder; clean up TODO

[Copilot]

Two medium-severity memory inefficiencies where large typed data was funnelled through number[] (8 bytes/element), causing ~9× peak memory overhead before final Uint8Array conversion.

Changes

src/utils/lzw.ts — M5

• LZWDecoder.decompress() replaced number[] accumulator with a doubling Uint8Array buffer
• Entries appended via buf.set(entry, len) (bulk) instead of byte-by-byte push()
• Returns buf.slice(0, len) to release the oversized backing buffer and allow GC

src/formats/tiff.ts — M6

• Both encode() and encodeFrames() now keep compressed pixel frames as Uint8Array chunks; only the small IFD section (~hundreds of bytes) is built in a number[]
• Final output assembled with a single pre-allocated Uint8Array + set() calls — eliminates the intermediate JS number array for pixel data entirely

// Before: byte-by-byte copy of entire compressed frame into number[]
for (let i = 0; i < pixelData.length; i++) result.push(pixelData[i]);

// After: direct set into pre-sized output buffer
out.set(frame, pixelPos);

TODO.md

Removed all verified-complete items (C1–C3, H1–H4, M1–M4, M7, L5). Remaining open: M5/M6 (now addressed above) and L1–L4, L6–L8.

CHANGELOG.md

Added entries for M5 and M6 under [Unreleased].

[Copilot]

Pull request overview

Reduces peak memory usage in two hot paths by eliminating large intermediate number[] byte accumulators, replacing them with Uint8Array-based buffering and final assembly via pre-sized typed arrays. This aligns with the project’s focus on efficient binary image encode/decode paths.

Changes:

• Refactored LZWDecoder.decompress() to write into a growable Uint8Array instead of a number[].
• Refactored TIFF encode() / encodeFrames() to keep compressed pixel data as Uint8Array chunks and assemble output via a single preallocated Uint8Array.
• Cleaned up TODO.md and added [Unreleased] changelog entries for the memory improvements.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
TODO.md	Removes completed items and marks M5/M6 as fixed.
src/utils/lzw.ts	Implements a growable Uint8Array output buffer for LZW decompression.
src/formats/tiff.ts	Avoids pixel data copying into number[]; assembles final TIFF bytes with Uint8Array.set().
CHANGELOG.md	Documents the LZW/TIFF memory improvements under [Unreleased].

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.