Return BadImage for a truncated image

[adamtheturtle]

Fixes #3498.

Image.verify raises OSError as well as SyntaxError — for example on a
PNG whose IDAT data is present but whose IEND chunk is missing.
Image.open succeeds for such a file, so validate_image_is_image does not
reject it first, and the bare OSError escaped the request: the mock failed
to respond at all.

validate_image_integrity now catches both. open_image runs outside the
try, so anything which cannot be opened at all is still rejected by
validate_image_is_image.

Verification

make_truncated_png_file builds the file from the reproduction in the issue.
New TestImage::test_truncated tests for add_target and update_target
fail with OSError: truncated PNG file without the fix and pass with it, on
the in-memory mock, the in-memory Docker application and real Vuforia — real
Vuforia answers 422 BadImage, so the mock now matches.

The Query API needs no change: it never calls verify, and real Vuforia
accepts the same truncated PNG there, returning an empty match list. Checked
against a live account.

The new update_target test needed a ci_pattern entry; the add_target
one is already covered by the TestImage pattern.

🤖 Generated with Claude Code

https://claude.ai/code/session_01H7tNiBpHomY5ShxZjQyWsf