[FEATURE] Add session labeling/tagging for better session management

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Currently, claude code --resume lists sessions by timestamp only, making it
difficult to distinguish between different types of work in the same
directory (e.g., frontend vs backend vs testing sessions).

Proposed Solution

Add the ability to label/tag sessions:

```bash
# Option 1: Tag on creation
claude code --tag frontend

# Option 2: Tag on resume
claude code --resume --tag frontend

# Option 3: List sessions with tags
claude code sessions list

Alternative Solutions

• Using separate directories (but same codebase)
• Manual notes (error-prone)

Would love to see this feature to improve workflow organization!

Priority

High - Significant impact on productivity

Feature Category

CLI commands and flags

Use Case Example

When working on a full-stack project, I want to maintain separate
conversation contexts for:

• Frontend development (Vue/TypeScript)
• Backend development (Django/Python)
• Testing and QA

Additional Context

Screenshots or mockups

Current behavior when multiple sessions exist:
[Session selection showing only timestamps]

1. 2025-01-17 14:30
2. 2025-01-17 10:15
3. 2025-01-16 18:45

Proposed behavior:
[Session selection with tags]

1. [frontend] 2025-01-17 14:30 - Vue component development
2. [backend] 2025-01-17 10:15 - API endpoint implementation
3. [testing] 2025-01-16 18:45 - E2E test setup

### Similar features in other tools

• tmux: Named sessions (tmux new -s frontend)
• VS Code: Workspace-specific settings
• Git branches: Named contexts for different work

### Technical considerations

• Session metadata could be stored in .claude/sessions/
• Backward compatibility: Existing sessions default to "default" tag
• Could integrate with git branch name as auto-tag