feat: Add status bar display options (original/shortened/hidden)

[Remilia-Kirisame]

What this PR does

Adds a "Status bar display" dropdown setting with three modes:

• Original — Paste Mode: Markdown (default, preserves current behaviour)
• Shortened — PM: MD (compact labels via a StatusBarLabel mapping)
• Hidden — hides the status bar item entirely

Related to #40

Changes

• Added StatusBarLabel lookup object (after Mode enum) for shortened display names
• Added updateStatusBar() helper to centralise status bar text + visibility logic
• Added statusBarDisplay to DEFAULT_SETTINGS (string: "original" | "shortened" | "hidden")
• Replaced the 3 individual setText calls with updateStatusBar() calls
• Added "Status bar display" dropdown in the Settings tab

How to test

1. yarn && yarn build
2. Copy main.js to .obsidian/plugins/obsidian-paste-to-current-indentation/
3. Reload Obsidian
4. Open Settings → Paste Mode
5. Change "Status bar display" between Original / Shortened / Hidden
6. Verify the status bar updates immediately for each option
7. Switch paste modes and verify the status bar reflects the correct mode
   in each display style

Tests I have done

• Test above
• Switch paste modes — the status bar updated correctly in each display style
• Click the status bar — the mode selector popup works
• Restart Obsidian — the setting persists
• Tested basic paste functionality (paste text in a few modes to confirm nothing is broken)