rebuildPlatformCatalogEmbeddings

Maintenance (requires write). Refreshes the search index over every platform catalog (MCP tools, whiteboard stencils, architecture icons, infographic templates, whiteboard design components and design skills), so that search by meaning in searchTools, listWhiteboardStencils, listArchitectureIcons and the design skill and component browsers stays current. Incremental: it scans every catalog and re-indexes ONLY the entries that changed (a cheap no-op when nothing changed). This normally runs automatically every hour, so manual calls are rarely needed; use it to force an immediate refresh after changing any catalog. Handles up to ~120 changed entries per call; if more changed, call again until allDone is true. Not part of normal authoring flows.