fix(cli): support multi-skill search installs

[christso]

Summary

• switch skill search TTY mode from single-select to searchable multiselect
• install all selected repos in one scope with a single sync and dedupe repo installs
• format interactive star counts with a space between the star and number

Validation

• bun run lint
• bun test
• bun run build

Manual E2E

1. ./dist/index.js skill search skill-source-mapping
   • verified the interactive picker shows ★ 1 with a space
2. ./dist/index.js skill search pr-search --limit 10
   • selected multiple entries in the searchable multiselect
   • confirmed the flow prompted for one install scope and installed multiple plugins in one sync

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