[Amazon Q] Add custom chat tab naming and hide/show functionality

## Summary
Request for enhanced chat tab management in Amazon Q Developer: custom naming and hide/show functionality.

## Problem Statement
Our development team of 12 engineers actively uses Amazon Q Developer. **8 out of 12 team members** requested these features in our recent retrospective, making this our most requested enhancement.

### Current Issues:
- Generic tab names ("Chat 1", "Chat 2") require manual inspection to identify conversations
- 5-8 concurrent conversations create visual clutter and navigation difficulty
- 15-20 seconds lost per context switch, occurring 20+ times daily per developer
- Important conversations get lost among numerous unnamed tabs

## Proposed Solution

### 1. Custom Tab Naming
- Right-click context menu: "Rename Chat Tab"
- Keyboard shortcut support (F2)
- 30-50 character limit
- Auto-save functionality
- Optional: Smart naming suggestions

### 2. Tab Visibility Controls
- Right-click option to hide/show tabs
- Hidden tab indicator badge
- Quick access dropdown for hidden tabs
- Keyboard shortcuts (Ctrl+H to hide, Ctrl+Shift+H to show all)
- Session persistence across IDE restarts

## Expected Benefits
- **60% reduction** in context-switching time
- **50% reduction** in visual clutter
- Improved conversation continuity and focus
- Better knowledge organization and sharing

## Use Cases
**Multi-Project Developer:**
- Names: "ProjectA-Auth", "ProjectB-Database", "Learning-React"
- Hides learning tab during active development

**Research & Development:**
- Names: "API-Research", "Performance-Debug", "Code-Review"
- Hides research tabs when debugging

## Environment
- VS Code with Amazon Q extension
- Team size: 12 developers
- Heavy Amazon Q usage across multiple projects

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*This enhancement would significantly improve workflow efficiency for teams using Amazon Q extensively.*

No implementation files, entry points, or tests are identified in the issue, so first locate the Amazon Q chat-tab UI in the VS Code extension and review its existing tab state and persistence behavior. Done should cover custom naming, hide/show controls, the listed shortcuts, hidden-tab access, and persistence across IDE restarts, with tests for the specified behavior.

Written by the indexing model from the issue text.