feat(flate): extract group-scoped DEFLATE into moq-flate / @moq/flate

[kixelated]

Summary

Extracts the per-group DEFLATE codec added in #1897 out of moq-json into a standalone, dependency-light crate moq-flate (and a matching @moq/flate npm package), so any framed-stream library can reuse it without the JSON snapshot/delta layer. The Rust and JS codecs stay wire-interoperable (raw DEFLATE + the RFC 7692 sync-flush marker trick).

This is a pure refactor of the codec plus a small consumer optimization. No wire-format change, so existing tracks (and the hang catalog) and the browser peer are byte-identical on the wire.

What changed

New moq-flate crate (rs/moq-flate)

• Encoder / Decoder moved over verbatim, made pub. Configurable DEFLATE level (Encoder::with_level) and decompressed-size cap (Decoder::with_max_frame_size), with DEFAULT_LEVEL / DEFAULT_MAX_FRAME_SIZE consts.
• Own Error (Decompress, TooLarge, #[non_exhaustive]).

New @moq/flate package (js/flate)

• pako-based Encoder / Decoder with { level } / { maxFrameSize } options. pako (+ fflate for the corruption test) move here from @moq/json.

moq-json / @moq/json

• Depend on the flate packages; their compression modules are deleted.
• Rust Error now wraps moq_flate::Error transparently (Flate(#[from] …)), replacing the Decompress / TooLarge variants.
• @moq/json's public exports are unchanged (it never re-exported the codec).

Late-joiner backlog collapse (moq-json consumer)

• Consumer::poll_next now applies every frame already buffered in the group in one poll, but yields only the latest reconstructed value and deserializes once. Frames are still decoded in order (the DEFLATE window and merge patches are sequential); only the per-frame deserialize + yield are skipped. A late joiner catches up to the head in one step instead of replaying every superseded state; live consumers keeping up still see each update. Mirrored in the JS consumer behavior via existing tests.

Example

• rs/moq-json/examples/telemetry.rs (cargo run -p moq-json --example telemetry): measures real wire savings on a realistic telemetry stream (~91% smaller with snapshot+delta+deflate) and asserts every tick round-trips (live + late joiner).

Public API changes

• New: moq-flate crate (Encoder, Decoder, Error, Result, DEFAULT_LEVEL, DEFAULT_MAX_FRAME_SIZE); @moq/flate package (Encoder, Decoder, options + default consts).
• Breaking (moq-json, Rust): Error::Decompress and Error::TooLarge(u64) removed in favor of Error::Flate(moq_flate::Error). The enum is already #[non_exhaustive], so external matches keep compiling via their wildcard arm.
• No change to @moq/json's exported surface.

Versioning

Bumps moq-flate / @moq/flate to 0.1.0 and moq-json / @moq/json to 0.1.0. These are hand-edited because release-plz never promotes a 0.0.x crate to 0.1.0 on its own.

Branch targeting

Targets main: the codec being refactored only landed on main (#1897) and is not on dev, so this can't be based on dev. The moq-json Error change is technically breaking, but moq-json is 0.0.x with no external consumers and the 0.1.0 bump marks the change intentional. Happy to redirect if you'd rather hold it for dev.

Cross-package sync

rs/moq-flate ↔ js/flate kept in lockstep (wire-interoperable, mirrored tests). rs/moq-json ↔ js/json updated together.

Test plan

• cargo test -p moq-flate (7) and -p moq-json (31) pass
• bun test js/flate (9) and js/json (45) pass
• tsc + Biome clean; cargo fmt --check + clippy clean via nix
• cargo run -p moq-json --example telemetry reports savings and verifies round-trips

(Written by Claude)

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 54c8651d-14a3-45d8-a577-f7b1daa16fc5

📥 Commits

Reviewing files that changed from the base of the PR and between a7c937e and e7f0874.

⛔ Files ignored due to path filters (2)

• Cargo.lock is excluded by !**/*.lock
• bun.lock is excluded by !**/*.lock

📒 Files selected for processing (19)

• Cargo.toml
• js/CLAUDE.md
• js/flate/README.md
• js/flate/package.json
• js/flate/src/index.test.ts
• js/flate/src/index.ts
• js/flate/tsconfig.json
• js/json/package.json
• js/json/src/compression.test.ts
• js/json/src/consumer.ts
• js/json/src/producer.ts
• package.json
• rs/CLAUDE.md
• rs/moq-flate/Cargo.toml
• rs/moq-flate/src/lib.rs
• rs/moq-json/Cargo.toml
• rs/moq-json/examples/telemetry.rs
• rs/moq-json/src/compression.rs
• rs/moq-json/src/lib.rs

✨ Finishing Touches

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch claude/sad-chebyshev-8488b5

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