[disassembler]

When Mithril downloads and verifies a snapshot but snapshot conversion fails, Daedalus currently discards the downloaded blocks. Retrying repeats the same failing conversion, while syncing from genesis downloads the blockchain again.

Add Keep blocks and replay ledger to the conversion error screen. This retains the verified immutable blocks, discards the unusable ledger/LSM state, and starts the node to rebuild its ledger locally. It supports first bootstrap, partial sync, and rebuilds, with English and Japanese copy. The option is available in the current watchdog session; retry, cancellation, and explicit genesis sync remain available.

Installation continues to use the existing network checks and interrupted-install safeguards. Replay omits the clean sentinel so the node validates the retained blocks. The PR includes the feature specification, plan, and task checklist.

Verification

• 363 watchdog unit tests passed.
• 19 Mithril regression integration tests passed; all six conversion-recovery integration tests passed after the final changes.
• 244 focused Jest tests passed across MithrilSyncContainer, BackendStore, and WatchdogManager.
• TypeScript compilation, Clippy with warnings denied, treefmt, and translation descriptor consistency checks passed.

Tests

• Recovery tests cover retaining staging, replay after bootstrap/partial sync/rebuild, no second download, removal of stale ledger state, explicit genesis selection, and retry/cancel.
• Renderer tests restrict the replay action to conversion failures and verify command dispatch.