refactor: rename Step Library → Solutions Library site-wide

User-facing text updated across page title, sidebar, command palette,
quick launch, quick actions, post-step modal, empty state, and
procedural editor. File paths/component names unchanged — those
will be renamed when the full Solutions Library feature ships.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/step-library/StepLibraryBrowser.tsx

@@ -269,8 +269,8 @@ export function StepLibraryBrowser({ onInsert, onCreateNew, showCreateButton = f
           ) : (
             <EmptyState
               illustration={<StepLibraryIllustration />}
-              title="Build a reusable step library"
-              description="Save common troubleshooting steps once, reuse them across flows. Keeps your team consistent and saves build time."
+              title="Build your solutions library"
+              description="Save proven resolutions from troubleshooting sessions. Your team's knowledge grows with every ticket solved."
               action={
                 onCreateNew ? (
                   <Button onClick={onCreateNew}>Browse Steps</Button>