fix: preserve registration when sync bootstrap fails

[SeaOceanO]

Summary

• finalize the accepted identity and bearer session before starting Sync V2 bootstrap in both Python and TypeScript
• keep a bootstrap failure recoverable through the existing id init-sync command and report that recovery action explicitly
• add behavioral regressions proving the remote registration runs once, local identity/session are published, pending registration is cleared, and the same Sync installation can be completed afterward

Why

Previously, a successful remote registration followed by a bootstrap timeout left only pending keys and no identity.json or session.json. id init-sync could not load that state, while retrying registration called the remote register method again with an often one-time OTP.

Verification

• Python: Ruff format/lint, strict mypy, 167 passed, 1 skipped, 7 deselected
• Python repository contracts: 7 passed
• Python sdist and wheel build passed
• TypeScript: Prettier, ESLint, typecheck, 102 tests across 15 files, and build passed
• git diff --check

Scope

This is a four-file recovery-order hotfix with no new state format, command, dependency, or runtime abstraction. It prevents new stranded registrations; it cannot reconstruct bearer tokens from failures that occurred before this fix because those tokens were never persisted.