feat: move conversations between workspace folders

[TroyMitchell911]

Summary

• atomically rebind a top-level conversation and its persisted open tab to another folder
• preserve the original transcript cwd while the next ACP resume uses the destination folder
• reject moves during an active turn and detach idle connections before rebinding
• add header/sidebar move UI for registered folders or any accessible directory
• keep local and remote tab runtime identities stable across migration
• localize the workflow in all 10 supported languages

Behavior

The source directory may still exist or may already be gone. Multi-hop moves retain the first origin, and moving back clears the origin marker. Same-folder requests are true no-ops. Chat, loop, and delegation-child conversations remain ineligible.

Tests

• 11 backend transaction, validation, event-order, CAS, and ACP lifecycle regressions
• authenticated HTTP route integration test with camelCase payload
• dialog, header snapshot, sidebar eligibility, tab convergence, workspace event, transport, and i18n regressions
• full Rust suite: 3099 passed, 2 ignored across library and integration targets
• full frontend suite: 5174 passed across 368 files
• server and desktop clippy with warnings denied
• full ESLint, Next.js production build, and desktop cargo check

Related context: #326, #453, #459, #552