### Summary
Adds accept/reject tracking for Mercury edit predictions.
### Changes
Sends events to https://api-feedback.inceptionlabs.ai/feedback when:
Accept — user presses Tab
Reject — user presses Escape
Ignore — prediction dismissed implicitly (typing, cursor move, etc.)
Added `discard_explicit` method to the delegate trait to distinguish
explicit vs implicit dismissal. Updated `reject_prediction` and
`reject_current_prediction` methods with an `explicit` bool parameter to
thread this through to the Mercury feedback logic. Other providers are
unaffected—they use the default implementation.
Feedback is fire-and-forget in a background thread, only sent for
predictions that were shown.
### Data Collected
- Request ID (returned from Inception API)
- User action (either accept/reject/ignore)
- Client Zed version (to track updates made to Zed client which could
potentially affect nextedit implementation)
Release Notes:
- N/A
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Co-authored-by: Ben Kunkle <ben@zed.dev>
