docs: record why task 15d attempt 1 was rejected

The attempt passed the gate and dropped Portuguese from the largest page
on a bilingual site: it scraped the legacy full-guide <main> at build
time with `?raw` and `set:html` instead of assembling the page from
the 19 block components and the content collections. That also couples
the new page to a file task 20 deletes.

Adds the constraint explicitly, lists the blocks by name so the next run
does not have to discover them, and adds two done-when boxes the gate
cannot check for it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

plans/astro-refactor/task-15d-page-full-guide.md

@@ -130,3 +130,52 @@ They are yours. Lift them verbatim — same rule as everything else, both locale
 mandatory, no retranslation, copy the exact strings out of `app.js`. Whether
 they become a seventh collection or an inline constant in the page is your call;
 say which you chose and why.
+
+## The first attempt was rejected — read this before you start
+
+Commit `a264d01` (tagged `rejected/15d-attempt-1`) passed the full gate with 42
+assertions intact and is still wrong. It did this:
+
+```js
+import legacyGuide from '../../full-guide/index.html?raw';
+let guideMarkup = legacyGuide.match(/<main>[\s\S]*<\/main>/)?.[0] ?? '';
+```
+
+and then `<div id="full-guide" set:html={guideMarkup} />`, mounting the four
+islands on top of the scraped markup. Three things that breaks:
+
+1. **Portuguese is gone.** The page contains zero `data-language-content`
+   attributes and zero `.pt` reads — every server-rendered detail panel
+   hard-codes `.en`. The legacy `<main>` is English-only; today's Portuguese
+   comes from `app.js`, which the Astro page does not load. The language
+   contract in `.agents/context/content-i18n.md` is binding and this violated
+   it. On a bilingual site's largest page, half the content vanished and the
+   gate said green.
+2. **Zero of task 10's block components are used.** All 19 exist in
+   `src/components/blocks/`. See the list below.
+3. **It couples the new page to the file task 20 deletes.** `/full-guide/` would
+   break the moment the legacy tree goes.
+
+**You may not read `full-guide/index.html` at build time.** Read it to learn
+what to build; do not import it, scrape it, or `set:html` it. The page's markup
+comes from components and content collections.
+
+### The blocks you are assembling from
+
+`src/components/blocks/`: `ChangeLens`, `ChapterHero`, `ComparisonTable`,
+`FileTabs`, `FleetDiagram`, `GridGroup`, `HandoffTable`, `PhasePanel`,
+`PreviewPane`, `ReviewDetail`, `RouteCard`, `RouteTable`, `SectionGrid`,
+`SiteFooter`, `SkillList`, `SkillPackage`, `TopBar`, `VoteWidget`,
+`WorktreeMap`. Plus `src/components/primitives/`. Read each one's props before
+you use it; several carry comments naming the legacy selector they replace.
+
+If a section of the guide has no block that fits, say so in your report and
+render it inline in the page — do not invent a new block, and do not fall back
+to scraping.
+
+### Two extra done-when boxes
+
+- [ ] Every localized string rendered twice, `data-language-content="en"` and
+      `"pt"`, per `.agents/context/content-i18n.md`
+- [ ] Zero imports of any file under `full-guide/`, and no `set:html` of legacy
+      markup