docs: verify the base path on the real host

The real-host smoke test was the migration's #1 production-only failure mode and
had never run. It has now run, without taking the site down: the Astro dist was
published to `pages` additively under two previously-unused paths (`_astro/` and
`_verify/summary/`), so all ten live pages stayed up, then force-pushed away.

Astro's base-prefixed absolute asset URLs resolve on the Pages Server — that was
the actual risk, and it is now proven rather than assumed. Trailing-slash
redirects match `trailingSlash: 'always'`.

Also corrects two things the guide got wrong:

- a `?v=$(git rev-parse --short HEAD)` cache-busting idiom. The Pages Server
  caches for ten minutes keyed on path, so a query string never busted it; the
  guide was telling operators to trust a check that could not work. A file you
  just deleted keeps serving 200 until the cache expires.
- the claim that a push to `main` publishes. It no longer does, and must not
  until cutover.

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

plans/astro-refactor/HANDOVER.md

@@ -78,10 +78,11 @@ tasks 05 and 06.
 
 ## Still open from task 01's own report
 
-- Real-host smoke test of `/ai-for-dummies/summary/` never ran — the branch is
-  not merged and CI has not published. **This is the #1 production-only failure
-  mode in the whole migration.** Do it before trusting any page work.
-- No Playwright locally, so screenshot comparison could not run in CI.
+- ~~Real-host smoke test of `/ai-for-dummies/summary/`~~ — **done**, see
+  "Resolved: the base path serves correctly on the real host" above.
+- No Playwright locally, so screenshot comparison still cannot run anywhere.
+  `visual-regression.mjs` also has no compare mode, so it is out of CI until it
+  grows one. See `.agents/rules/gates.md`.
 
 ## The decision that is still yours
 
@@ -94,24 +95,44 @@ external-CSS assertion. See `.agents/context/design-system.md`.
 
 ## Next steps, in order
 
-1. **Decide the font question** (see below). It blocks task 19 and it is the
+1. **Decide the font question** (see below). It blocks task 19 and it is now the
    only thing here that needs a human.
-2. Push `main` — nothing has left this machine yet. Safe now: the `publish` job
-   is `workflow_dispatch`-only, so pushing no longer overwrites the live site.
-   Watch that first CI run; the act-runner has never executed a job.
-3. Once CI is green, do the real-host smoke test of `/ai-for-dummies/summary/`.
-   **This is still the #1 production-only failure mode in the migration** and it
-   has not been done. Publish manually via the workflow's `publish` input, on a
-   throwaway basis, or accept the risk until task 20.
-4. Clean up the four merged worktrees and branches.
-5. Fan out phase 1 and 2:
+2. Fan out phase 1 and 2:
    ```bash
    .agents/scripts/launch.sh 05 content-guide   --base main
    .agents/scripts/launch.sh 06 content-review  --base main
    .agents/scripts/launch.sh 07 primitives      --base main
    ```
    All three are unblocked now that 02 and 04 are in `main`. After 07 lands,
-   08–11 run four at a time.
+   08-11 run four at a time. **Task 07 is the routing calibration point** -
+   judge it before committing to MiniMax for the other twelve.
+3. Clean up the four merged worktrees and branches in `~/Projects/af-task-0*`.
+   `~/Projects/af-task-02/before/` holds 29 MB of misplaced untracked
+   screenshots; delete or move them first.
+
+## Resolved: the base path serves correctly on the real host
+
+This was the #1 production-only failure mode and it is now **verified against
+the live Pages Server**, not just `pnpm run preview`.
+
+Method, which is reusable and costs no downtime: the Astro `dist/` was published
+to the `pages` branch **additively** — `_astro/` plus a single page at
+`_verify/summary/`, both paths previously unused, so no existing file was
+touched and all ten live pages stayed up throughout. Results:
+
+- `/ai-for-dummies/_verify/summary/` → 200, and it really is the Astro page
+  (`<title>AI For Dummies — Route map</title>`), not a 200-ing error page.
+- `/ai-for-dummies/_astro/chapters.PwjFDHFw.css` → 200 `text/css`. **This is the
+  actual base-path proof**: Astro emits base-prefixed _absolute_ asset URLs, and
+  the server resolves them.
+- `/ai-for-dummies/_verify/summary` (no trailing slash) → 307 to the slashed
+  form, which matches `trailingSlash: 'always'`.
+
+The probe was force-pushed away immediately; `pages` is back at `37a1e48`.
+
+Note for whoever publishes next: **the Pages Server caches for ten minutes**,
+keyed on path. A deleted file keeps serving 200 until the cache expires, and a
+`?v=<sha>` query does not bust it. See `docs/operations-guide.md` step 6.
 
 ## Carried over from the phase 0 review