Simplify schema version caching to manifest-first

[VisLab]

Follows up the manifest fast path by removing the now-redundant directory-scoped commit-SHA gating from the REST fallback. The manifest is the primary version-discovery path; the fallback is now a plain ETag-cached crawl used only for custom URLs or when the manifest can't be read. Also drops the repo_check_interval parameter (its only purpose was the gating). Net −373 lines; tests/docs/CHANGELOG updated.

[Copilot]

Pull request overview

This PR simplifies HED schema version discovery by making the repo-level schema_versions.json manifest the primary path, and by removing the directory-scoped commit-SHA “gating” from the REST API fallback (including dropping the now-redundant repo_check_interval parameter). This reduces complexity in hed_cache.get_available_hed_versions() while keeping a plain ETag-cached crawl as a fallback for custom URLs or manifest failures.

Changes:

• Removed directory-level commit-SHA gating (and related cache keys/constants) from the REST fallback and dropped the repo_check_interval argument.
• Updated get_available_hed_versions() documentation to describe the manifest-first behavior and the REST fallback behavior.
• Updated tests/docs/changelog to reflect the new caching/version-discovery approach.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/schema/test_hed_schema_io.py	Removes tests tied to commit-SHA gating/repo_check_interval and updates expectations around cached URLs.
hed/schema/hed_cache.py	Removes commit-SHA gating logic and repo_check_interval; uses manifest-first discovery with ETag/time throttling via cache_time_threshold.
hed/schema/init.py	Updates module docstring to reflect manifest-first listing behavior.
docs/user_guide.md	Updates user guide caching section to describe manifest-first behavior and REST fallback tiers; removes repo_check_interval example.
CHANGELOG.md	Updates release date and describes manifest-first discovery and fallback behavior changes.