Fix CMAP palette bounds in Amiga ILBM decoder

[segrax]

Motivation

• Prevent an out-of-bounds write when decoding ILBM CMAP chunks into the fixed 256-entry sImage::mPalette which could be triggered by crafted/oversized CMAP chunks in attacker-controlled assets.

Description

• Add a bounds check (if (i < 256)) around writes to Result.mPalette[i] in Source/Amiga/Graphics_Amiga.cpp::DecodeIFF while continuing to consume CMAP bytes so parsing behavior for valid assets is preserved.

Testing

• Ran git diff -- Source/Amiga/Graphics_Amiga.cpp && git status --short to verify the change and it reported the expected diff; the command succeeded.
• Committed the change with git add Source/Amiga/Graphics_Amiga.cpp && git commit -m "Fix CMAP palette bounds in Amiga ILBM decoder" and the commit succeeded.
• Inspected the patched lines with nl -ba Source/Amiga/Graphics_Amiga.cpp | sed -n '600,635p' to confirm the bounds check is present and that command succeeded.

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Codex Task