Complete Linux desktops, engine recovery, and agent sandboxes for 0.4.6

[Augani]

Summary

• completes the Apple-silicon Linux desktop runtime, including accelerated VirGL/Venus rendering, display/input, audio, microphone, camera, clipboard, scrolling, device telemetry, and isolated renderer/filesystem workers
• fixes first-launch engine recovery, doryd machine list, server provisioning, data-drive authority, Docker credential/plugin repair, VM socket paths, component download/install, and machine readiness
• distinguishes Desktops from headless agent Sandboxes and adds durable named sandbox sessions, templates, recipes, dependency discovery, and repair workflows
• componentizes the optional Linux desktop payload while keeping Docker Core self-contained
• advances the app to 0.4.6 (build 52), updates usedory.dev project metadata, and incorporates the issue/PR fixes reviewed during qualification

Verification already completed locally

• full Swift package and app test suites
• Rust workspace tests and security audit after the ChaCha 0.10.2 lock update
• Developer-ID signed 0.4.6 candidate build with exact renderer/kernel/component verification
• release, component, doctor, host CLI, and security contract suites

Release note

Public asset publication remains fail-closed until the exact signed component candidate is connected to post-build physical Linux VM qualification. This PR intentionally does not bypass that release safety boundary.