cdrom: fix cdread_2048 writing the sector header into the wrong buffer

[nicolasnoble]

cdread_2048 writes the sync pattern and MSF into the caller's dest, but the
mode byte, subheader and EDC/ECC into the member scratch m_cdbuffer. readTrack
passes m_cdbuffer as dest so the two alias there and it never showed; every
other caller, in practice every Lua read through CDRIsoFile, gets bytes 15..23
and the EDC/ECC tail as leftover garbage. GUESS then reads the bogus mode byte,
falls through to RAW, and hands back the sync pattern where user data should be.

Verified against an ISO9660 image: GUESS on sector 16 now returns the CD001
volume descriptor instead of the sync pattern.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 2da5bf34-019a-4f5c-9441-70dc6defb3e7

📥 Commits

Reviewing files that changed from the base of the PR and between 3e10093 and ab8e456.

📒 Files selected for processing (1)

• src/cdrom/cdriso.cc

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📝 Walkthrough

Walkthrough

cdread_2048 now writes generated sector headers and EDC/ECC data directly to the caller-provided dest buffer.

Changes

CD-ROM sector buffer generation

Layer / File(s)	Summary
Generate sector data in destination buffer src/cdrom/cdriso.cc	cdread_2048 writes sector header fields and computes EDC/ECC in dest instead of m_cdbuffer.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly explains the buffer-writing defect, affected callers, resulting behavior, and verification.
Title check	✅ Passed	The title clearly and concisely identifies the cdread_2048 buffer-writing defect.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Fix failing CI checks

🧪 Generate unit tests (beta)

• Create PR with unit tests

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