Refresh measles featured analysis: add a 'doing this today' assistant section and fix citation/metadata bugs

## Summary

The measles featured analysis — [_Evolutionary dynamics of coding overlaps in measles virus_](https://brc-analytics.org/learn/featured-analyses/evolutionary-dynamics-of-coding-overlaps-in-measles) (source: `sites/brc-analytics/docs/learn/featured-analyses/evolutionary-dynamics-of-coding-overlaps-in-measles.mdx`, dated 2025-10-29) — needs two kinds of update:

1. Its LLM methodology predates BRC-analytics' own integrated AI assistant and is now out of date.
2. A closer read surfaces several citation and metadata bugs.

This page reads as a published manuscript (fixed author list, citable Galaxy history, Zenodo workflow DOI, companion videos). The intent here is **not** to rewrite the science or retroactively change what was done — the original methodology and videos should stay intact as the historical record. The goal is to (a) add a short "doing this today" note so the workflow doesn't look dated, and (b) fix factual/citation defects.

## 1. Add a "Doing this today" section (LLM methodology refresh)

The article describes LLM-assisted interpretation as a manual, two-browser-window copy-paste loop:

> "…a setup shown in Fig. 5 in which we used two open browser windows: one with Galaxy workspace and another with ChatGPT, Microsoft CoPilot, Claude, or any other LLM agent capable of writing python code" (§ _Making sense of variants_)

and twice notes the notebooks were "generated entirely using ChatGPT." Since this was written, BRC-analytics has shipped its own **integrated AI analysis assistant** (feature flag removed in #1527, 2026-08-02), and the field has moved to agentic, tool-using assistants. The two-window copy-paste setup in Figure 5 is now the pre-assistant way of working.

**Proposal:** leave the original narrative and Figure 5 as the record of what was done in 2025, and add a short callout / subsection — e.g. "Doing this today" — that:

- Points readers at the built-in BRC-analytics assistant as the current path for the same ad-hoc, overlapping-reading-frame analysis, instead of an external chatbot in a separate window.
- Notes the shift from copy-pasting snippets to an in-product, provenance-aware assistant.
- Keeps the existing safety guidance ("LLM-generated code should ALWAYS be treated with extreme caution and made publicly available") — that message is still correct and worth retaining.

## 2. Content bugs found on review

### Citations
The inline bracket-citation numbering is broken in the evolutionary-analysis section (§ _Comparative analysis of substitution effects_ and Fig. 8 discussion):

- **[8] resolves to two different sources** — `pubmed/18385234` and `pmc/PMC2395192`.
- **[12] is used for two different papers** — `doi/10.1038/nature16933` (ancestral-state reconstruction, Methods) and `pubmed/18562542` (Y110H).
- **[14] is used for two different papers** — `pubmed/17686504` and `pubmed/19007958`.
- **[13] and [14] both point to `pubmed/19007958`** — the text has adjacent `[13] [14]` citing the same paper.
- **[16] is missing** — the sequence jumps [15] → [17].
- **No bibliography / Sources section exists.** All references are inline bracket-links with no resolved reference list, so a reader can't map e.g. [17] to a citation. (The Learn blog posts include a full Sources list; this page should match.)

### Metadata / freshness
- **Frontmatter `description: ""` is empty** — hurts SEO and social-link previews. Add a 1–2 sentence description (same gap being fixed on the Cyclospora blog posts).
- **Stale catalog counts** — "At the moment of writing [BRC-analytics] listed 1,601 genome assemblies corresponding to 1,149 distinct pathogen, host, and vector taxa" is a self-dating figure. Refresh the numbers or reword to be version-neutral.

## Suggested checklist

- [ ] Add a "Doing this today" callout pointing at the integrated assistant (keep original methodology + videos intact)
- [ ] Fix duplicated/colliding citation numbers ([8], [12], [13]/[14])
- [ ] Resolve the missing [16] in the sequence
- [ ] Add a resolved References/Sources section
- [ ] Fill in the empty frontmatter `description`
- [ ] Refresh or de-date the assembly/taxa counts

Because several of these touch authored scientific prose (citations, the LLM narrative), the fix should go through author review rather than a drive-by PR.

Open sites/brc-analytics/docs/learn/featured-analyses/evolutionary-dynamics-of-coding-overlaps-in-measles.mdx and review its frontmatter, methodology, citation links, and assembly-count wording. Check the integrated assistant context described in #1527, then ensure the callout, corrected citations, resolved Sources section, description, and counts are complete while preserving the original 2025 narrative and videos for author review.

Written by the indexing model from the issue text.