app: Citation + Validation Guidelines accordions, validation link in About

Bundle 1+2 C7. Two collapsed accordions above the leaderboard
tables plus a validation-policy bullet on the About tab.

- Validation Guidelines accordion (collapsed by default, sits above
the tables). Carries the two-tier story in two lines
(unvalidated -> validated, four evidence types) plus a link to
the canonical policy doc in the main repo at
`cadgenbench/docs/benchmark/validation.md`. Bundle 4 creates the
file; the link will 404 until that lands, then resolves.
- Citation accordion (collapsed by default, below Validation
Guidelines). Carries the verbatim BibTeX entry locked in
space-setup/bundles/1-2-space-ux.md (cite key cadgenbench2026,
Space URL as howpublished). Rendered in a `gr.Code` with
language=None (no BibTeX highlighter ships with gradio) and
show_line_numbers off so the entry stays copy-paste tidy.
- About tab picks up a new bullet linking the same validation doc.

VALIDATION_DOC_URL is centralised at module level so the
Validation Guidelines markdown, the About bullet, and any future
caller stay in sync.

Verification (autonomous):

- 19/19 unit tests still green.
- Local boot probe: GET /config returns JSON containing both
accordion labels ("Citation", "Validation guidelines"), the
BibTeX cite key ("cadgenbench2026"), the validation doc URL,
and the About-tab validation bullet. Report proxy still serves
200 + text/html for a known modern row.

Live probe runs after push; will surface only on failure.

app.py

@@ -47,6 +47,14 @@ logging.basicConfig(
 )
 
 
+# Canonical policy doc lives in the code repo so contributors reading
+# the GitHub repo see it without needing to visit the Space. Linked
+# from both the Leaderboard tab's Validation Guidelines accordion and
+# the About tab.
+VALIDATION_DOC_URL = (
+    "https://github.com/huggingface/cadgenbench/blob/main/docs/benchmark/validation.md"
+)
+
 ABOUT_MD = f"""## About
 
 **CADGenBench** evaluates AI-driven CAD generation: how well a model can
@@ -61,8 +69,26 @@ correct 3D model.
   submissions and computed results in
   [`{HF_SUBMISSIONS_REPO}`](https://huggingface.co/datasets/{HF_SUBMISSIONS_REPO}).
 - **Code**: [`huggingface/cadgenbench`](https://github.com/huggingface/cadgenbench).
+- **Validation policy**: [`docs/benchmark/validation.md`]({VALIDATION_DOC_URL}).
 """
 
+# Verbatim BibTeX entry locked in space-setup/bundles/1-2-space-ux.md
+# (Locked decisions section). Shown in the Citation accordion as a
+# copy-paste handle for anyone citing this benchmark; the About tab
+# already links the source code via huggingface/cadgenbench so the
+# Space URL is the right deep-link target for the citation.
+CITATION_BIBTEX = r"""@misc{cadgenbench2026,
+  author       = {Rabinovich, Michael and {Hugging Face}},
+  title        = {{CADGenBench}: a benchmark for {AI}-driven {CAD} generation},
+  year         = {2026},
+  publisher    = {Hugging Face},
+  howpublished = {\url{https://huggingface.co/spaces/HuggingAI4Engineering/cadgenbench-leaderboard}},
+}"""
+
+VALIDATION_GUIDELINES_MD = f"""Submissions appear on the **Unvalidated** table the moment evaluation completes. Maintainers promote rows to **Validated** after methodology review, accepting one of four evidence types (`code`, `traces`, `api`, `manual`).
+
+Full policy: [`docs/benchmark/validation.md`]({VALIDATION_DOC_URL})."""
+
 DETAIL_PLACEHOLDER = "_Click a row above for details._"
 
 _ISO_TS_RE = re.compile(r"^(\d{4}-\d{2}-\d{2})T(\d{2}:\d{2}):\d{2}Z$")
@@ -221,6 +247,22 @@ with gr.Blocks(title="CADGenBench Leaderboard", theme=gr.themes.Soft()) as block
     )
 
     with gr.Tab("Leaderboard"):
+        # Collapsed accordions above the tables. Validation guidelines
+        # gives the short two-tier story + link to the full policy
+        # doc; Citation carries the verbatim BibTeX entry. Both start
+        # closed so the leaderboard itself stays above the fold.
+        with gr.Accordion("Validation guidelines", open=False):
+            gr.Markdown(VALIDATION_GUIDELINES_MD)
+        with gr.Accordion("Citation", open=False):
+            # language=None -> plain monospaced render (gr.Code doesn't
+            # ship a BibTeX highlighter); show_line_numbers off because
+            # the entry is meant to be copy-pasted, not annotated.
+            gr.Code(
+                value=CITATION_BIBTEX,
+                language=None,
+                show_line_numbers=False,
+            )
+
         # Two stacked tables, split by `validation_status`. Validated
         # on top so the curated results are above the fold; unvalidated
         # below carries every other row (auto-published, awaiting