storage-resize-images kit tracking issue #3263

Tracks parity between the storage-resize-images extension (0.3.6) and the @firebase-function-kits/storage-resize-images kit.

How it was tested: both deployed side by side on a test project with matching configs and driven with the same uploads, then compared on output images, metadata, paths, deletes, events, content filtering, logs, regions, install, reconfigure and uninstall. Kit tested at 0.0.2-rc.7 (kits @ fcdd555), installed with functions:kits:install. ext:migrate and the interactive install prompts are not covered yet.

Resize output, metadata, paths, include and exclude lists, delete modes, bad-input handling and loop guards matched the extension in every case tested.

Also affects this kit: #3256 (blank required params fail the deploy, shared by all kits) and #3168 (unknown IMAGE_TYPE values).

Existing extension bugs that the kit carries over are tracked separately, not as sub-issues: #3269 (a malformed reply to CUSTOM_FILTER_PROMPT blocks the image) and #3270 (content filter failures in a region without the model don't name the region).

Sub-issues are ordered by priority, highest first.

Issues labelled decision need a call: change the kit, or record the difference as accepted in the below "Decisions" section.

Decisions

• decision(storage-resize-images): kit/extension parity – event source is per function, not per instance #3272: the kit's event source is the function's service, not the extension instance. Accepted and documented in docs(storage-resize-images): document the kit's event source #3306.
• decision(storage-resize-images): kit/extension parity – FUNCTION_DEFAULT_REGION is required but BUCKET_REGION overrides it #3274: FUNCTION_DEFAULT_REGION is required and only used when BUCKET_REGION is empty. Accepted and documented in docs(storage-resize-images): document FUNCTION_DEFAULT_REGION #3307.