read_range_utf8 used the infer-based ForgeFS::is_binary (MIME sniff over 8192 bytes, assumes text when the type is unknown), while fs_search, fs_write, plan_create, and image_read all used the BOM + zero-byte detector in binary_detection.rs. A file with a stray 0x00 in the first 512 bytes was skipped as binary by search but read as text by read_range_utf8.

This PR routes read_range_utf8 through the same is_binary(path) detector used by every other caller, and removes the now-unused infer-based implementation, its tests, and the infer dependency.

Files changed:

• crates/forge_fs/src/read_range.rs: use is_binary(path_ref) instead of Self::is_binary(&mut file); add regression test
• crates/forge_fs/src/is_binary.rs: deleted (no remaining callers)
• crates/forge_fs/src/lib.rs: remove mod is_binary;
• crates/forge_fs/Cargo.toml: remove infer dependency

Fixes #3633

Verification

• cargo test -p forge_fs --lib passes (10 tests, including new test_stray_zero_byte_classified_as_binary)
• cargo clippy -p forge_fs --lib is clean
• cargo check -p forge_infra and cargo check -p forge_app pass (no downstream breakage)