fix(desktop): change name in dock from harper-desktop to Harper

[elijah-potter]

Issues

Fixes #3477

Description

Updates Harper Desktop's user-facing macOS app name from harper-desktop to Harper without changing the underlying product/package identity used for generated artifacts.

• Adds bundle.macOS.bundleName in harper-desktop/src-tauri/tauri.conf.json so the macOS bundle/Dock display name is Harper.
• Updates the main editor window title in harper-desktop/src-tauri/src/lib.rs from harper-desktop to Harper.
• Leaves productName, bundle identifier, updater endpoint, package names, and config paths unchanged to avoid renaming CI artifacts or changing app identity.

Demo

N/A

How Has This Been Tested?

N/A; this PR only changes Tauri display metadata and the main window title.

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.

[hippietrail]

Closes #3477 by the way.

[elijah-potter]

Added to the description. Thank you!