perf: optimize SNES identifier to read only ~66KB instead of full file

[wizzomafizzo]

Summary

• Optimize SNES identifier to read only the necessary header data (~66KB max) instead of the entire ROM file (256KB-6MB)
• Detect SMC header presence by checking file size rather than reading the full file first
• Provides approximately 100x reduction in I/O for SNES files

Background

The SNES identifier was reading the entire ROM file when it only needs to read up to the HiROM header location (0xFFC0 + 32 bytes). This matches the behavior of the original Python GameID implementation.

Changes

• Calculate read offset to skip 512-byte SMC header if present (detected via size % 1024 == 512)
• Only read up to snesHiROMHeaderStart + snesHeaderSize bytes (~66KB)
• ID generation remains identical to before

Test plan

• All existing unit tests pass
• Lint passes with 0 issues
• Tested against real SNES ROM files in ZIP archives

[codecov]

Codecov Report

❌ Patch coverage is 77.77778% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
identifier/snes.go	77.77%	1 Missing and 1 partial ⚠️

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