* fix(tagging): Images tag search goes through the tag index (#379, PR 3)
The Images Tags filter and text search no longer stream every image tag
row per request. image_tag_ids reads the names that tag at least one image
(exact under Tags, case-folded substring for q) and image_tag_locators
reads their files by tag_id through idx_media_image_tags_tag. Results are
unchanged: a differential test compares the lookup with the old stream,
and a trace test checks that no statement reads media_image_tags except
by tag id. The search contract in TESTING.md and a browser test (CUJ 8)
follow.
Closes#379
* test(search): pin prompt-only tags and multi-chunk tag lookups (#379)
Reads the tag names and the locators in the same annotation read helper.