1## Tasks23- [x] Add `semantic_diff` field to changed file entries in `_spec_browser()` payload4- [x] Add view-mode toggle (semantic / side-by-side / raw) to `SpecsView` component in dirty/refs modes5- [x] Render `SpecDeltaView` when semantic mode is selected for changed files6- [x] Keep "current" mode unchanged (no diff, just SpecContentView)7- [x] Test: dirty mode shows semantic diff for changed specs8- [x] Test: refs mode shows semantic diff for changed specs9- [x] Test: view-mode toggle persists across file selection within a session