Verify sentence case compliance for all UI text

[Claude]

Obsidian bot flagged UI text not using sentence case. Comprehensive audit confirms all 26 UI text strings already comply.

Verification scope

• Context menu items (3): "Open in terminal", "Open in PowerShell", "Open in CMD"
• Settings sections (2): "Context menu items", "Executables"
• Setting names (8): All follow sentence case with proper capitalization of proper nouns (PowerShell, CMD, Windows, macOS, Linux)
• Setting descriptions (8): First word and proper nouns only
• Placeholders (5): Follow lowercase command/filename conventions

All capitalizations are justified by sentence-initial position, proper nouns, or acronyms. Previous PR #8 already addressed this issue.