fix(elements): accept <glyph-camera> alias as scene's parent

[apresmoi]

Problem

The HTML usage from the landing/README snippets (and the new /api/html doc) fails at runtime:

```html
<glyph-camera rot-x="0.4">
...

```

```
Uncaught Error: glyphcss: must be placed inside a or .
```

`elements.ts` registers `` as a subclass of `GlyphOrthographicCameraElement`, but `GlyphSceneElement._findCameraAncestor` walks the ancestor chain comparing `tagName` against only `glyph-perspective-camera` / `glyph-orthographic-camera`. The alias subclass keeps its own `glyph-camera` tag name, so the check misses it.

Fix

• Add `glyph-camera` to the allowed tag list in `_findCameraAncestor`.
• Update the error message to mention the alias.
• New test: scene mounts inside `` without throwing.

Test plan

• `pnpm --filter glyphcss test` — 174/174 passing
• `pnpm build` — packages + website both green
• Manual: paste the HTML snippet from README into a sandbox after next publish; no console error