[dajiaohuang]

Summary

GlobalStore::add hashes a graph source before the configured graph-size check runs during parsing. file_hash used fs::read, temporarily allocating the complete source file even when the import is later rejected for exceeding the cap.

Hash the file in fixed 64 KiB chunks, preserving the existing first-16-hex SHA-256 key. Retry interrupted reads and propagate other I/O errors. Add a multi-chunk Rust regression and an independent SHA-256 comparison to the Graphify parity harness.

Verification

• cargo fmt --check: passed.
• Focused file_hash Rust test: passed.
• Strict Clippy with Rust 1.95, default features: passed.
• Full default Rust suite: 338 passed, 4 failed, 3 ignored. The failures are in existing Windows path/Golang extractor tests, outside this change.
• Required postgres,bedrock,transcription feature Clippy could not compile because this environment has no OpenSSL development installation (openssl-sys failure).
• The Graphify parity harness could not start because its pinned reference/Graphify-Labs__graphify-0.9.95 source directory is absent in this checkout.

No dependency changes. CI was not queried.