feat(ux): enhance search discoverability and status accessibility

[AhmmedSamier]

This PR implements several micro-UX improvements to enhance the accessibility and discoverability of DeepLens features:

1. Status Bar Accessibility: The status bar item now has an accessible name (DeepLens Index Status) and a tooltip that explicitly indicates it is clickable ("Click for stats").
2. Search Filter Clarity: The filter buttons in the search interface now have descriptive tooltips (e.g., "Files (/f) - Search files by name") instead of just labels, helping users understand the scope.
3. Context-Aware Empty States: When a search yields no results within a specific scope, the message now explicitly states the scope (e.g., "No files found" vs "No results found"), reducing confusion about whether the search failed or just the filter was too restrictive.
4. Feature Discovery: Added /cmd (Commands) and /e (Endpoints) to the "Welcome" list to ensure users are aware of these powerful search capabilities.

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PR created automatically by Jules for task 14928927892086094627 started by @AhmmedSamier

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