Fix stale frame routing in hotkey and speed control flows

[CMJNB]

Background

After page navigation or iframe recreation, stale frame IDs can remain in media cache.
This may cause hotkeys or speed-related messages to be sent to dead frames on first attempt.

Changes

• Improved media auto-selection:
  • Added content-script liveness check for the final candidate.
  • If the selected frame is stale, remove the corresponding m:scope:tabId:frameId entry and reselect.
• Improved media event delivery:
  • Check target frame availability before sending.
  • Fallback to frameId=0 when the original frame is unavailable.
• Improved temporary speed delivery:
  • Applied the same frame liveness check and fallback strategy to temporary-speed messages.

Scope

• Only affects media message routing and frame-id recovery logic.
• Does not change speed/lastSpeed context semantics or toggle strategy.
• Other command behaviors remain unchanged.

Files

• src/background/utils/getAutoMedia.ts
• src/utils/configUtils.ts
• src/background/utils/processKeybinds.ts

Validation

• Local build passes (npm run dev).
• Stale-frame scenarios now recover by rerouting to a live frame.

[CMJNB]

Thanks for the fix and iteration, really appreciate the effort.
Two small notes for reference:

1. Some parts of this change may still be a bit inconsistent in coding style. If possible, could we do a light cleanup pass later? Sorry for the extra ask.
2. I have tested this for a full day on the websites that usually expose this issue, and the previous problem is now mostly gone; that said, I think it still makes sense to keep monitoring for a while.