Phase 2 AI visibility: pilot content-sharing conversion (IA migration de-risk)

## Why this matters (IA context)

This supports the broader **job-led information architecture (IA)** improvement
tracked in #7230 and kicked off in #7232. Before migrating engine and deployment
content into the new task-oriented sections at scale, we pilot the chosen
content-sharing mechanism on a small set of real pages to confirm it holds up —
both in reader UX and in keeping one clean, citable copy per concept. The pilot
de-risks the larger IA migration.

## Goal

Pilot the chosen sharing mechanism on the highest-occurrence `show-in`/`hide-in`
pages: convert them to the inverted model, verify reader UX and rendered output,
and confirm the approach before any bulk migration.

**Blocked on the #7233 route decision** and the mechanism spike. The exact
conversion steps depend on the chosen route.

Parent: #7230 · IA migration: #7232 · Decision: #7233 · Design: `docs/exec-plans/active/2026-06-03-ia-sharing-canonical-validation-design.md`

## Candidate selection

Rank `show-in`/`hide-in` pages by occurrence and pick the top handful:

```sh
grep -rlE '\{\{%\s*(show-in|hide-in)' content/ \
| while read f; do echo "$(grep -cE '\{\{%\s*(show-in|hide-in)' "$f") $f"; done \
| sort -rn | head
```

(Note: the shortcodes use `{{% %}}`, not `{{< >}}`.)

## Tasks

- [ ] Select top-N pages from the ranking above
- [ ] Convert each to the chosen route (authoritative real page + consumer
references/includes), removing conditionals from the authoritative copy
- [ ] Add 301 redirects for any moved URLs
- [ ] Verify rendered output (Cypress + visual review of the preview pages)
- [ ] Capture lessons in the design doc before proposing bulk IA migration

## Out of scope

- Bulk migration of all shared pages (follow-up after the pilot)
- The route decision (#7233) and mechanism scoping (spike)

Start with the #7233 route decision and the mechanism spike, then read docs/exec-plans/active/2026-06-03-ia-sharing-canonical-validation-design.md. Rank the show-in/hide-in occurrences under content/ using the provided command, select the top pages, and convert them according to the decided route. Done means redirects, Cypress and preview verification, and lessons captured in the design document.

Written by the indexing model from the issue text.