docs: rename pages.mdx component visibility key to visibleWhen

[os-warren]

Fixes#129

What changed

content/docs/build/interface/pages.mdx was the last English page spelling the
page-component conditional-visibility key as visibility instead of the
ADR-0089 canonical visibleWhen. Renamed it in both places:

• Line 81 — the Components code example: visibility: "..." → visibleWhen: "...".
• Line 98 — the component property-table row: key renamed, and the description
  now keeps a one-line note that visibility is still accepted as a
  deprecated alias, since it genuinely parses and normalizes at the schema
  boundary and silence would read as "my metadata just broke" to an existing
  author.

Editorial-call note (per the card): I looked for an established corpus
convention for documenting an accepted-but-deprecated alias inside a
property-table row and found none — the one precedent
(content/docs/build/automation/approvals.mdx) documents its deprecated
alias in prose above the table, not as a table row annotation, and links to
matching os lint rule ids. Since no table-row precedent exists, I followed
the PM triage recommendation: a short parenthetical note in the description
cell rather than a separate row or silence.

English source only — no locale siblings touched. pages.zh-Hans.mdx is now
reported stale by the translation freshness gate, which is the designed
non-blocking behavior (see below).

Premise re-verification (on branch point 5fd04d8)

content/docs/build/interface/pages.mdx:81: visibility: "'sales_manager' in os.user.positions",
content/docs/build/interface/pages.mdx:98:| `visibility` | `string` | CEL visibility predicate |

Corpus grep for the three spellings across English .mdx (locale siblings
excluded) confirms this was still the only visibility:/`visibility`
hit, with a visibleWhen/visibleOn control probe returning real hits
elsewhere (formulas.mdx, validation-rules.mdx, views.mdx,
changelog.mdx) — the single-hit reading is a real measurement, not a
broken grep.

Verification (HEAD 94b76e5)

• pnpm turbo run type-check --filter=@objectos/docs --force — 1 successful, 1 total.
• pnpm turbo run build --filter=@objectos/docs --force — 1 successful, 1 total; confirmed the rendered /en/docs/build/interface/pages.html output contains visibleWhen in both the code sample and the property table, with the deprecated-alias note.
• node .github/scripts/check-translations.mjs — exit 0, "✓ translations gate passed"; pages.zh-Hans.mdx now listed as stale, which is the designed non-blocking outcome (English lands on its own; the next translation pass re-derives it).
• pnpm turbo run test was not run — it executes zero tasks in this repo.

Generated by Claude Code

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Generated by Claude Code