0764f0e563
When users switch from pinned version to tag in opencode.json (e.g., 3.10.0 -> @latest), the cache package.json still contains the resolved version. This causes bun install to reinstall the old version instead of resolving the new tag. This adds syncCachePackageJsonToIntent() which updates the cache package.json to match user intent before running bun install. Uses atomic writes (temp file + rename) with UUID-based temp names for concurrent safety. Critical changes: - Treat all sync errors as abort conditions (file_not_found, plugin_not_in_deps, parse_error, write_error) to prevent corrupting a bad cache state further - Remove dead code (unreachable revert branch for pinned versions) - Add tests for all error paths and atomic write cleanup