docs: add Apify glossary page linked from the footer

[marcel-rbro]

Adds a single A–Z glossary of Apify-specific terms at /glossary.

Not in the page tree

The sidebars in sources/platform/sidebars.js are autogenerated per directory (get-started, actors, storage, proxy, integrations, account, security). This page sits at the root of sources/platform/, outside all of them, so no sidebar picks it up and it adds nothing to the navigation tree. Verified in the build output: the page renders with no sidebar container, and /glossary appears in no sidebar menu on any page.

It is reached from the Reference column in the footer instead, added in apify-docs-theme/src/config.js. Happy to move it to the "For AI" column if that reads better — see the open questions below.

Scope

Apify-specific concepts plus the proxy family. Terms common to web scraping and software development in general (web scraping, crawling, session, JSON, headless browser) are deliberately left out — they add no Apify-specific value and every entry we keep is one more thing to maintain.

Each entry is one sentence that links to the page owning the concept, so the glossary routes rather than duplicates. The linked page stays canonical, which keeps drift low.

32 terms, one ## heading each, so every term gets a stable anchor (/glossary#dataset) that other pages can link to. toc_max_heading_level: 2 keeps the table of contents to the term list.

Agent readability

The page is picked up automatically by the llms-txt plugin — no separate pipeline. Confirmed in the build output:

• listed in llms.txt under a ## Glossary category (added a routeRules entry in docusaurus.config.js, otherwise it fell through as lowercase glossary)
• full content in llms-full.txt
• .md counterpart served at /glossary.md
• present in sitemap_base.xml

Verification

• docusaurus build passes, exit 0, zero broken links (onBrokenLinks is throw)
• Every internal link checked against the slug: front matter on master
• vale --minAlertLevel=error: 0 errors
• markdownlint: clean

Open questions

1. Footer column — Reference (current) or "For AI", next to llms.txt?
2. Do the three newer terms belong in v1 — Apify AGI, x402, and webhook? They're all documented, but they're the least settled entries here.
3. Top-level redirect — the URL is already /glossary, so no redirect is needed. Flagging only in case there's a reason to also keep a path under /get-started.
4. Naming — entries follow standards/terminology.md casing, so concept terms are lowercase (build, dataset, schedule) while product names are capitalized. That makes the A–Z list mixed-case. Worth a look.

A previous Academy glossary was removed in #2130 on SEO grounds (low traffic, generic web-scraping terms). This one is deliberately different: Apify-specific vocabulary only, agent-first, and kept out of the navigation, so it isn't competing for the same traffic.

Draft — opening for direction on the four questions above before polishing the wording.

[apify-service-account]

✅ Preview for this PR (commit 8fec708) is ready at https://pr-2976.preview.docs.apify.com (see action run).