Templatize ambiguous-link inline rendering (mirror #221 for RRTAmbiguous)

[srid]

#221 moved the inline rendering of broken (Rel.RRTMissing) wikilinks from a hard-coded Pandoc AST in Emanote.Pandoc.Renderer.Url.renderSomeInlineRefWith into a Heist template at templates/components/broken-link.tpl. The sibling Rel.RRTAmbiguous arm in the same function still builds B.Strikeout, B.Str "❗", and one Diagnostic.errorInlineAside "aside" per candidate route in Haskell.

The two arms are structurally the same concern ("this link cannot be resolved, tell the user"), and they used to share their AST shape. After #221 they diverge:

• RRTMissing ↦ templates/components/broken-link.tpl, semantic class hooks (emanote:broken-link__*), notebook authors override structure by dropping in their own .tpl.
• RRTAmbiguous ↦ Haskell-built AST, emanote:error:aside consumed by pandoc.rewriteClass, no template seam.

Hickey/Lowy review on the #221 PR called the asymmetry out. The defer reason then was narrow: ambiguous-link rendering iterates over a list of candidate routes (variable length), and a list-of-candidates Heist splice protocol does not exist yet — broken-link's flat fixed structure didn't need one.

Scope of this issue:

• Design a list-splice protocol so a template can iterate the candidate routes (each with its own URL, label, and openInNewTabAttr decision).
• Add templates/components/ambiguous-link.tpl matching the existing RRTAmbiguous output.
• Migrate RRTAmbiguous in Emanote.Pandoc.Renderer.Url to the same HE.lookupHtmlTemplateMust + HE.runCustomTemplate pattern Add .tpl for rendering broken wikilinks, so the user can override it #221 introduced.
• Decide whether pandoc.rewriteClass for emanote:error:aside (only consumer left after Add .tpl for rendering broken wikilinks, so the user can override it #221 lands) stays, gets renamed for symmetry with emanote:broken-link__aside, or is retired in favour of inlined Tailwind utilities (matching Add .tpl for rendering broken wikilinks, so the user can override it #221's choice).

Out of scope: anything outside the two Url.hs arms.