feat(languages): redesign language pack manager

[fcoury]

The language-pack picker made descriptions and an empty preview pane more prominent than the packs themselves, defaulted to the custom-source action, and expanded far beyond the content it displayed. Native grammar approval also needed a focused surface that made the exact approved bytes explicit.

This redesigns the language-pack workflow around compact, task-focused dialogs:

• present pack names as the primary rows with aligned catalog metadata, hidden-description search, curated-first ordering, and intrinsic responsive sizing
• add focused install and management action sheets, catalog retry feedback, and continuous completion states
• move native grammar approval into a safe-default confirmation that shows the source and exact SHA-256 digests
• bind installed-package approvals to the confirmed grammar set and bytes so a change between review and approval fails closed

Builds on #174.

How to Test

1. Start Red with no language packs installed, run :plugins, and wait for the catalog.
   • Go and Swift appear before + Add custom source….
   • Go is selected, metadata is right-aligned, no preview appears, and the dialog fits its content.
2. Select Go and choose Install with syntax highlighting.
   • The confirmation lists the repository, resolved commit, and exact grammar digest.
   • Back is selected by default; approving installs the pack and returns to the manager with completion feedback.
3. Resize the terminal to a narrow width and reopen :plugins.
   • Pack names remain intact while metadata collapses to the version-only form.
4. Make the catalog unavailable and retry.
   • A selected Retry official catalog row appears and Enter starts another refresh.
5. Choose Add custom source… and install a pack with a native grammar.
   • Highlighting remains disabled until the exact installed grammar bytes are approved.