geotiff: raise on malformed IFD chain pointing past EOF (#1863)

[brendancol]

Summary

• parse_all_ifds now raises ValueError when an IFD chain offset points beyond the end of the file. The previous silent break could mask corrupt overview metadata in truncated or malformed TIFFs.
• Behavior matches the existing MAX_IFDS guard a few lines down.
• Closes geotiff: parse_all_ifds silently truncates IFD chains pointing past EOF #1863.

Test plan

• Malformed chain with next_ifd_offset >= len(data) raises ValueError.
• Malformed file with first_ifd_offset >= len(data) raises ValueError.
• Boundary case next_ifd_offset == len(data) raises.
• Big-endian variant raises.
• Valid chains (next_ifd_offset == 0) still terminate cleanly.
• Existing IFD/header tests still pass (92 total in the sweep).

[Copilot]

Pull request overview

Replaces the silent break in parse_all_ifds with a ValueError when an IFD chain offset points past EOF, so malformed TIFFs are surfaced rather than masked as truncated-but-valid chains. Updates the existing related test and adds a dedicated test module.

Changes:

• Raise ValueError in parse_all_ifds for offsets >= len(data).
• Update TestClassicTIFFLargeOffset to expect the new exception.
• Add comprehensive tests covering header first_ifd_offset, next_ifd_offset, boundary, big-endian, and valid-terminator cases.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
xrspatial/geotiff/_header.py	Replace silent break with ValueError on past-EOF IFD offset
xrspatial/geotiff/tests/test_header.py	Update existing test to expect ValueError
xrspatial/geotiff/tests/test_parse_all_ifds_malformed_chain_1863.py	New tests covering malformed IFD chain scenarios

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