[Docs/Perf] Per-element getBimElement() doesn’t scale — document bulk reads #94

Environment

• vim-web 1.0.0-alpha.0, IIFE build (dist/vim-web.iife.js) loaded via <script>
• API: VIM.Core.Webgl.createViewer() (headless, custom UI)
• Chromium / desktop, devicePixelRatio 1.75
• Model: 2,547 elements (2,264 with geometry), 12 Revit categories, structural

Summary. The documented per-element path (element.getBimElement()) is fine for a handful
of elements but pathological for whole-model work. Reading the BIM tables in bulk is ~3 orders
of magnitude faster.

Measured (2,264-element model, same machine):

// Per element — the "obvious" path
await Promise.all(els.slice(0,100).map(e => e.getBimElement())); // >30s, timed out ❌

// Bulk — via the VimDocument tables
await Promise.all([
  vim.bim.element.getAllName(),
  vim.bim.element.getAllCategoryIndex(),
  vim.bim.element.getAllFamilyName(),
  vim.bim.element.getAllId(),
  vim.bim.category.getAllName(),
]);                                                              // ~13ms for the whole model ✅
// map with el.element (BIM index): names[el.element], catNames[catIdx[el.element]], …

Asks.

• Document the bulk vim.bim.<table>.getAll*() pattern as the recommended approach for
  iterating many elements, and call out that getBimElement()/getBimParameters() are
  per-element conveniences not meant for full-model loops.
• Consider a batched vim.getBimElements(indices?) that resolves an array in one pass.