fix github actions build

[Tsyklop]

This branch overhauls how framework lessons persist and propagate learner changes across stages, replacing the legacy diff-based storage with a git-like content-addressable history (snapshots / commits / refs), and fixes the resulting navigation, course-update, and submission flows. It also gets CI and the :intellij-plugin:test suite back to green.

Why
The legacy diff-based framework storage lost or mis-propagated learner code across stages (ALT-10961, ALT-10998, ALT-10961 follow-ups). A self-contained snapshot history makes navigation/update deterministic and restart-safe, and fixes the data-loss bugs the failing tests captured.

What changed

1. Framework lesson storage — git-like architecture (ALT-10961)
   FrameworkLessonManagerImpl reworked to store full per-stage snapshots as content-addressable blobs with commits and stage_ / step_ refs and a HEAD (see framework/impl/FRAMEWORK_STORAGE.md). Full contents (not diffs) are stored so state survives IDE restart / offline.
   FrameworkStorage / LegacyFrameworkStorage / framework/storage/UserChanges updated; legacy records are migrated on the fly.
   Navigation propagation reworked: snapshot-based target state, ancestor checks to decide when a merge is needed, and a Keep / Replace conflict path (PropagationConflictDialog) with auto-Keep/auto-Replace heuristics based on whether each side has learner changes.
2. Course update preserves learner changes
   FrameworkTaskUpdateInfo, FrameworkLessonHistory, UpdateUtils: when a course update adds/removes/changes a framework task file, the learner's local edits are preserved instead of being overwritten; author content is kept in the task model for later revert.
3. Supporting changes
   SolutionLoaderBase, TaskNavigationAction, handlers/handlersUtils, HyperskillUtils, HyperskillOpenInIdeRequestHandler, submissions/utils, ext/TaskExt/StudyItemExt, VirtualFileExt adjusted for the new storage model (original test/template file caching, ref handling, rename/move).