feat(cli): add discovery, recommendation, and shared search workflows

[dogbertdev]

Summary

• add shared search-resolution helpers plus new plex recommend and richer search / playlist flows
• expand plex client discovery, metadata, smart-playlist, and match parsing support, including a sanitized real-response fixture
• add compact discovery output helpers on top of the existing advanced library discover surface and refresh the docs/tests around the new workflows

Testing

• go vet ./...
• go test -race ./...
• go build -v ./...
• repo pre-push hook (goimports, golangci-lint, go test ./...)