feat(desktop): get display name for bundles from system

[elijah-potter]

Issues

Fixes #3502

Description

This PR changes Harper Desktop integrations to display app names resolved by the Rust OS broker instead of deriving labels in the frontend from bundle ID suffixes.

Implements macOS system lookup in MacBroker for bundle IDs, falling back to a private safe suffix-based display name.

Demo

N/A

How Has This Been Tested?

Added Rust unit tests for private fallback display-name behavior.

AI Disclosure

• I am a human and didn't use any AI.
• I used LLM features of my editor, but not an agent.
• I used an AI agent interactively.
• I am an agent or I got an agent to do the work autonomously.

Checklist

• I have performed a self-review of my own code
• I have added tests to cover my changes
• I have considered splitting this into smaller pull requests.