Add malformed-input regression tests for LAC and WAV parsers

[audexdev]

Summary

Current tests cover happy-path roundtrips and a few top-level decoder errors, but malformed parser/decoder coverage is shallow. We need targeted regression tests for corrupted WAV and LAC structures.

Affected areas

• tests/test_e2e.cpp
• tests/test_zerorun.cpp
• new malformed-input test files if useful

Test cases to add

WAV:

• truncated RIFF header
• truncated chunk-size field
• fmt chunk smaller than 16 bytes
• data before fmt
• invalid byte_rate and block_align
• oversized declared data chunk with short payload
• odd-sized unknown chunks and padding

LAC/container/block:

• invalid block count
• oversized block table
• truncated block payload
• invalid per-block stereo flag
• unsupported predictor orders
• invalid residual modes and reserved tags
• zero-run overflow beyond partition size
• trailing bytes after a valid stream

Acceptance criteria

• Each malformed fixture fails deterministically without crashes or excessive allocation.
• Tests do not require large binary files in the repository.
• Tests can run in CI without the ignored local assets/ directory.