fix(autopilot): soft-fail persistent sandbox startup

[ahmedhesham6]

Description

Allow autopilot to keep the server/gateway/scheduler online when persistent sandbox startup fails, while surfacing the startup error through health/status output. Also updates release Docker publishing to build native amd64/arm64 images and publish a multi-arch manifest.

Related Issues

None.

Changes Made

• Record persistent sandbox startup failures in server state and expose sanitized errors on /v1/health.
• Treat sandbox startup errors as a completed startup phase so stakpak up does not wait forever.
• Show sandbox startup failures in autopilot status and document the behavior in the system prompt.
• Ensure failed sandbox readiness terminates the spawned process.
• Split Docker release publishing into native amd64/arm64 image jobs plus a manifest smoke test.

Testing

• rustfmt --edition 2024 --check on staged Rust files
• cargo clippy -p stakpak -p stakpak-server --all-targets -- -D warnings

Screenshots (if applicable)

N/A

Breaking Changes

None.

[kajogo777]

what happens if persistent sandboxes are enabled + sandbox flag is set for a schedule, will the agent run? or fail because the persistent sandbox failed to start?