Support compressed virtual chunk locations (needs fzstd dictionary support)

[Shane98c]

icechunk (earth-mover/icechunk#1776) introduced dictionary-compressed virtual chunk locations. The manifest FlatBuffer schema has location_dictionary, compression_algorithm, and compressed_location fields that we don't read yet.

Current state

• Our generated FlatBuffer classes already have the accessors
• Our dependency fzstd doesn't support dictionary decompression but there's an open PR adding it: Support loading a dictionary for decompression 101arrowz/fzstd#18
• Tried swapping to zstdify which has dictionary support but ran into issues I think related to fix(zstdify): correct sequence RLE decoding semantics bhouston/zstdify#3
• No upstream fixture data uses this feature yet

What's needed

• Wait for fzstd#18 to land and release
• Update manifest-parser.ts to read compressedLocation from ChunkRef
• Update manifest-parser.ts to read locationDictionary/compressionAlgorithm from Manifest
• Decompress locations at parse time (matching Rust impl), priority: compressed_location → location → chunk_id → inline
• Add tests (will need synthetic fixtures or wait for upstream data)

References

• Upstream schema: manifest.fbs — ChunkRef.compressed_location, Manifest.location_dictionary, Manifest.compression_algorithm

[tylere]

Given that https://github.com/101arrowz/fzstd hasn't been updated in 2 years, maybe its time to use the PR/fork that solves this (https://github.com/handlerug/fzstd/tree/push-qxkytkvukoqs)? If the PR gets reviewed/approved soon, you could switch back.

[Shane98c]

good call @tylere, seems like lots of folks are hitting this lately. I'll get a PR up and tested asap!