feat(embed): embed::flate, the low-level API absorbed from minizlib

[MagicalTux]

What

Adds compcol::embed::flate (needs embed + deflate), which is the full public API of the minizlib crate. Once this ships as 0.7.1, minizlib becomes a deprecated re-export of it, with no change to its API.

Unlike the Encoder / Decoder codecs, which own their window and table, this module uses only memory the caller provides:

• Decoding: gunzip / unzlib / inflate / decompress (autodetects gzip or zlib), and *_len to only count. Output goes into the caller's Buffer (which doubles as the history window), through a Stream window of any size, or into a Counter. Input is pulled through Reader (a callback), Bytes (an iterator) or any Input, or pushed into a Decompressor.
• Compressing: gzip / zlib / deflate, Compressor (one chunk at a time) and BufferedCompressor, all using a hash table the caller provides, of any size.
• Errors: its own Error, which keeps I/O failures (Io) and a too-small window (WindowTooSmall) apart from other errors.

minizlib's fine-grained features are fixed at their defaults:

• checksums are always verified;
• concatenated gzip members and all three block types are always decoded;
• CRC-32 uses the 16-entry table, shared with embed's own codecs.

Footprint

Seven flate configurations are added to tools/footprint. Their ceilings are documented in compcol::embed and README. None links any panic machinery, and the measurements match minizlib 0.1 to within a few bytes:

configuration	code	stack
gunzip, buffer out	2430	1376
gunzip, streams	2756	1520
gunzip_len	2288	1376
Decompressor	3460	1448
gzip, buffer out	982	160
Compressor, streams	1344	792
BufferedCompressor	1522	400

flate's CRC-32 and Adler-32 start from their standard initial values, not from all zeros. With all zeros, LLVM clears a Decompressor with memclr8, which links about 200 extra bytes.

Tests

minizlib's test suite is ported as tests/embed_flate_*.rs, and CI's embed test step now runs it.

• Round trips against flate2, a new dev-dependency.
• Every kind of input and output.
• Streams truncated and corrupted.
• Push input cut into pieces of every size.

These checks pass locally:

• fmt;
• clippy on --features all, --all-features, embed,gzip and embed;
• rustdoc with -D warnings;
• cargo test --all-features;
• the thumbv7em build;
• the MSRV 1.88 check;
• tools/footprint/check.sh.

🤖 Generated with Claude Code