Render provenance and citation markers as grouped icon asides - #180

Supersedes #166. Closes #148 (default shinychat citation UI) and closes
#149 (minimal markers) — the look #149 asked for, through the mechanism
#148 asked for.

Where things stand

Both PRs chase the same destination: small icon markers instead of
pills, with a one-shot pulse on mount. #166 gets there with commons-owned
CSS that restyles shinychat's compact-aside DOM state by state; this PR
gets there by changing what commons asks shinychat to render — labeled
identity asides — and confining commons CSS to shinychat's public
--shiny-chat-aside-marker-* theming variables.

How they compare, at a glance:

What this PR does

Conceptually, three moves:

• Citations render as labeled identity asides instead of compact
  numbered chips, so shinychat owns the marker entirely — grouping,
  overflow counts, popovers, and interaction states.
• All three markers (Verified, Untrusted, citation) render
  icon-only. The label stays in the DOM for the pill's aria-label,
  and commons CSS touches only shinychat's public
  --shiny-chat-aside-marker-* variables.
• Singleton citation popovers gain a body title (icon + source
  label), since shinychat only renders its own title row for grouped
  asides.

A local example app renders every outcome — including a three-citation
paragraph and a singleton citation — for manual comparison against the
review transcript. It's not part of the package; source below.

# Save as app.R and run with shiny::runApp().
#
# What a live commons chat renders for each provenance outcome:
# Verified and Untrusted answers end with a marker; Cited answers show
# their citation asides instead — including a paragraph with several
# citations, which shinychat accumulates into one marker with a "+N"
# overflow and a carousel popover. A fourth message carries a lone
# citation: shinychat only renders its popover title row for grouped
# asides, so commons puts its own title (icon + source label) at the
# top of the aside body to keep singleton popovers named too.

corpus <- list(
  list(
    label = "documentation",
    kind = "prose",
    text = "Revenue excludes tax and shipping."
  ),
  list(
    label = "sales table",
    kind = "schema",
    text = "Revenue is recognized at shipment, not at order placement."
  ),
  list(
    label = "measure definitions",
    kind = "definition",
    text = "Gross margin is net revenue minus cost of goods sold."
  )
)

citation <- function(quote, explanation) {
  render_citation_aside(quote, explanation, corpus)$html
}

ui <- bslib::page_fillable(
  theme = commons_theme(),
  shinychat::chat_ui(
    "chat",
    messages = list(
      list(
        role = "assistant",
        content = paste(
          "6 orders came in last week.",
          provenance_aside("A")
        )
      ),
      list(
        role = "assistant",
        content = paste(
          "Revenue excludes tax and shipping, is recognized at shipment,",
          "and feeds straight into gross margin.",
          citation(
            "Revenue excludes tax and shipping.",
            "Supports the definition given in the answer."
          ),
          citation(
            "Revenue is recognized at shipment, not at order placement.",
            "Supports the recognition timing."
          ),
          citation(
            "Gross margin is net revenue minus cost of goods sold.",
            "Supports the margin description."
          )
        )
      ),
      # A lone citation: shinychat only renders its popover title row
      # for grouped asides, so the aside body carries its own title
      # (icon + source label) to name the source here too.
      list(
        role = "assistant",
        content = paste(
          "Revenue is recognized at shipment, not at order placement.",
          citation(
            "Revenue is recognized at shipment, not at order placement.",
            "Supports the recognition timing."
          )
        )
      ),
      list(
        role = "assistant",
        content = paste(
          "Margins appear roughly flat. Treat this as an estimate.",
          provenance_aside("C")
        )
      )
    )
  )
)

server <- function(input, output, session) {}

shiny::shinyApp(ui, server)

Notes

• Icon concepts are transition from pills to badges #166's, with glyphs from Radix Icons (MIT).
  The warning mark is a white exclamation on the original yellow
  circle, matching transition from pills to badges #166. The citation mark is a "quote" glyph in
  white on a navy tile — transition from pills to badges #166's serif " text element was
  white-on-transparent, designed to sit on a solid dot, and its
  metrics shifted with font substitution; the redraw is a fixed
  <path>. The trusted mark is a "check" glyph in white on the
  green shield badge.
• Citations deliberately don't pulse. Verified and Untrusted keep
  transition from pills to badges #166's one-shot pulse (disabled under prefers-reduced-motion); the
  pulse should say "check this answer's provenance," not "this answer
  cites something."
• Cited answers keep their review marker here; transition from pills to badges #166 removes it.
  Live chat shows no Cited marker in either PR — the citation asides
  are the signal. But review transcripts don't recreate inline
  citations today, so removing the marker there would leave Cited
  answers indistinguishable from answers with no data activity. Worth
  revisiting once the (forthcoming) sibling replay PR lands citation
  asides in review.

Validation

Unit tests updated and passing (test-citations.R, test-provenance.R).
Browser tests updated for the new markup and passing
(test-citation-browser.R, 27 expectations against live chromote).
Manual check of the
example app above recommended for glyph placement, the stadium shape on
grouped markers, pulse timing, and dark mode (tone hexes were chosen
for light backgrounds).