feat: support safe manual plugin installs

[0717lee]

Summary

• classify verified install sources as npm, GitHub subdirectory, manual, or unsupported
• keep one-click installation restricted to verified npm package specs
• show verified non-npm sources as copy-only manual install instructions
• surface catalog/detail verification conflicts and refresh current catalog authorization before installation
• add regression coverage for source parsing, shell metacharacters, unsafe paths, and verification states

Security

Non-npm sources are never passed to the DSH installer process. Manual commands are generated only from a strict validated source grammar; unsupported source strings are not echoed back to users.

Validation

• npm run test:source (9 tests passed)
• npm pack --dry-run
• Host/Web bundles built in a DeepSeek Harness workspace with tsc --noCheck entry generation followed by pnpm --filter @sandbaseai/dsh-plugin-store bundle
• git diff --check

The full workspace tsc -b remains blocked by existing Harness remote type errors and the existing pluginInventory type mismatch; no new package-local type errors were reported after the changes.

Closes #10