Allow dismissing/snoozing individual items in the "My Work" tab

### Feature summary

Add the ability to dismiss, hide, or snooze individual items in the "My Work" tab so users can curate the list to reflect what they actually intend to act on, rather than the raw set of PRs/issues GitHub associates with them.

### What problem are you trying to solve?

The "My Work" tab currently surfaces every PR and issue tied to me (assigned, review-requested, authored, etc.). In practice this includes a lot of noise:

- PRs I've been added as a reviewer to but don't plan to review (e.g. the team has rotated ownership).
- Draft PRs or stale items waiting on someone else, where there's nothing for me to do right now.

Because I can't remove these from the view, the tab loses its value as a focused "what should I work on next" surface. The signal-to-noise ratio drops as the list grows, and important items get buried.

### Proposed solution

Add a per-item action on each "My Work" entry with options like:

- Dismiss: hide the item until its state changes on GitHub (new comment, review requested again, new commit pushed, etc.), at which point it reappears.
- Snooze until: hide for a chosen duration (e.g., 1 day, 1 week, until Monday, custom date).
- Hide permanently: remove until I explicitly unhide it.

Plus:
- A "Show dismissed/snoozed" toggle or section so hidden items aren't lost.
- An easy "Undo" immediately after dismissing.

### Workflow impact

This would make "My Work" function more like a real inbox instead of a read-only mirror of GitHub queries.

### Installation context

_No response_

### Additional context

_No response_

L’issue identifie l’onglet My Work, mais ne nomme aucun fichier, test ni point d’entrée de l’implémentation. Commencez par localiser cet onglet et la manière dont ses éléments sont chargés, puis clarifiez les règles de persistance et de réapparition pour dismiss, snooze, permanent hide, la vue des éléments masqués et Undo. Le travail est terminé lorsque le comportement sélectionné est implémenté de manière cohérente pour les éléments individuels.

Rédigé par le modèle d'indexation à partir du texte de l'issue.