chore: rename the app and repository to MeshCore Desktop

[kNoAPP]

Description

Renames the app to MeshCore Desktop and the repository slug to kNoAPP/MeshCore-Desktop.

Important

Rename the GitHub repository to MeshCore-Desktop before merging this PR. The Connect screen's GitHub link, the issue template's security advisory link and the gh calls in the agent skills all point at the new slug. They 404 until the rename happens, and GitHub's redirect only applies after it.

Display name

• Wordmark (header and desktop-only screen) now reads "MeshCore Desktop".
• app/layout.tsx title, manifest.webmanifest name and the service worker comment use "MeshCore Desktop". short_name stays "MeshCore".
• Locale strings that name the app (title.app, title.device, title.deviceUnread, notify.testTitle, desktopOnly.body) now say "MeshCore Desktop" in en/de/es/fr. Strings that name a radio or the protocol ("Connect your MeshCore Companion via USB cable", "MeshCore Companion Protocol") are unchanged.

Repository slug

• kNoAPP/MeshCore-WebAgent → kNoAPP/MeshCore-Desktop in every license header, LICENSE, AUTHORS, SECURITY.md, the issue template config, ConnectPanel's GitHub link, docs/identity-derivation.md, and the --repo / REPO= / GraphQL -f repo= arguments in the agent skills.
• Headings and clone instructions in README.md, CONTRIBUTING.md, AGENTS.md and .github/copilot-instructions.md.

Package and release

• package.json / package-lock.json name and release-please package-name → meshcore-desktop. Running npm install here also rewrote unrelated lockfile entries (a different npm/platform), so the lockfile diff is limited to the two name fields. npm ci --dry-run still accepts it.
• The release archive in deploy.yaml becomes meshcore-desktop-v${VERSION}.zip.
• webagent removed from cspell.json. desktop did not need adding.

Not renamed: IndexedDB meshcore, the meshcore-shell-v1 SW cache, the backup format, meshcore:// links and CHANGELOG.md, as the issue specifies.

Verified

• git grep -i webagent has no matches outside CHANGELOG.md, and every remaining MeshCore Companion match refers to the radio or the protocol.
• npm run build: out/index.html <title> and out/manifest.webmanifest name read "MeshCore Desktop".
• In npm run dev, the header wordmark and the browser tab read "MeshCore Desktop".
• spell-check, lint, type-check, build and Prettier all pass locally.
• There are no radio code paths in this change, so no hardware check was needed.

Before	After

Still to confirm after the repo rename: the Pages deploy and the develop ruleset still work, gh issue list --repo kNoAPP/MeshCore-Desktop works, and the next release asset is named meshcore-desktop-vX.Y.Z.zip.

Issues

• Closes chore: rename the app and repository from MeshCore-WebAgent to MeshCore-Desktop #452

Type of Change

• ❌ ! -- Breaking change (fix or feature that would cause existing
  functionality to change)
• ✨ feat -- New feature (non-breaking change which adds functionality)
• 🛠️ fix -- Bug fix (non-breaking change which fixes an issue)
• 📝 docs -- Additional or updated documentation
• 🎨 style -- Code style changes (formatting, missing semi colons, etc)
• 🧹 refactor -- Code refactor
• ⚡ perf -- Performance improvement
• 🧪 test -- Tests (adding or updating tests)
• 🏗️ build -- Build system or external dependencies changes
• ✅ ci -- Build configuration change
• 🗑️ chore -- Grunt tasks
• ⏪ revert -- Revert previous changes