fix(github): avoid caching empty release assets

[risu729]

Fixes #9520.

Summary

• add a cache initializer path that can return rejected values without storing them
• skip GitHub release-detail cache writes for releases whose asset list is empty
• ignore already-cached empty release details and refetch before using them

Tests

• cargo fmt --check
• cargo test github::tests
• cargo test cache::tests

[gemini-code-assist]

Code Review

This pull request introduces a conditional caching mechanism in CacheManager through the new get_or_try_init_async_if method. This functionality is applied to GitHub release fetching to prevent the caching of releases with empty asset lists, ensuring that incomplete data is not persisted. Feedback suggests refactoring the cache lookup logic to reduce code duplication and highlights a potential efficiency issue regarding the lack of concurrency synchronization during redundant fetch calls.

[greptile-apps]

Greptile Summary

This PR fixes a bug where GitHub releases with empty asset lists (e.g. due to GitHub propagation delays) were being cached, causing subsequent install attempts to fail without re-fetching. It introduces a conditional caching path on CacheManager and wires it into both get_release and get_release_for_url.

• Adds get_or_try_init_async_if to CacheManager: like get_or_try_init_async but skips populating the in-memory and on-disk caches when the fetched (or disk-cached) value fails a caller-supplied predicate, while still returning the value to the caller.
• Updates get_release and get_release_for_url to use the new method with should_cache_release, which rejects releases whose assets list is empty; both functions now also return an owned GithubRelease directly instead of cloning a &T reference.

Confidence Score: 5/5

The change is narrowly scoped to the GitHub release fetch path and is safe to merge.

Both modified functions are exercised by new tests covering the disk-cache bypass, fresh fetch, and in-memory cache hit. The logic in get_or_try_init_async_if correctly avoids setting either OnceCell with a rejected value. The return-type change from Result<&T> (with an explicit .clone()) to Result preserves the public API for all callers.

No files require special attention.

_{Reviews (4): Last reviewed commit: "Merge branch 'main' into fix/github-empt..." | Re-trigger Greptile}