Add one-click Doctor actions to Nova

[papi-ux]

What changed

• parse Doctor v2 evidence and actions from Polaris
• add one-click recheck, safe bitrate correction, and gradual quality restoration to the Nova Quick Menu
• automatically continue clean verification windows and expose Undo through the snackbar
• refuse bitrate reduction when a stale network label lacks current packet-loss or latency evidence

Why

Nova previously repeated the host diagnosis and checklist recommendation but could not safely resolve it. A stale jitter result could therefore tell the player to lower an already history-capped bitrate.

User impact

Doctor becomes an evidence-gated one-click workflow from the stream overlay. It explains the proposed action, applies it through the paired host, verifies the result, and preserves an immediate undo path.

Validation

• PolarisApiClientParsingTest
• NovaQuickMenuUiStateTest
• regression coverage for stale clean-network evidence and history-safe restoration
• git diff --check

Depends on the matching Polaris Doctor v2 endpoint change.