[transitrix]

Summary

• Adds library/index.html — the library section's index, listing every item present.
• Adds library/archimate-cheat-sheet/index.html — the sheet's content as readable HTML inside the site's normal page shell (head/meta/canonical/OG via the site conventions, header, theme toggle, footer, assets/css/style.css), reflowed for a screen rather than the fixed 297mm x 167mm print grid. Wording carries across unchanged: every element list, the relationship descriptions, the derivation rule, the "three pairs that get confused" notes, the bottom-strip cards, the trademark attribution and the print sheet's own footer lines. The PDF is offered as the prominent download, served unmodified (no regeneration, no transformation).
• Links the homepage to /library/ (new "Free reference material" section) so both new pages are reachable and indexable.
• Regenerates sitemap.xml to include both new pages.
• Fixes a crash in .github/workflows/indexing-declarations.yml's reachability crawler: it opens every linked local path as UTF-8 HTML to extract further links, and the sheet page's link to its own PDF is the first internal link to a non-HTML file on this site — it threw UnicodeDecodeError. A linked non-HTML file is now treated as a reachable leaf with no further links to follow.

Notes

• This branch is stacked on site: render a library item's PDF from its committed source #56 (itself stacked on site: fix the library's shape and no-gate contract #55, both still open) — the diff here includes their commits until those merge to main. Only the last commit is new.
• Page title is exactly ArchiMate cheat sheet (no | Transitrix suffix) per the epic's "no suffixes, no campaign wording" constraint on a library item's page title — the library index page keeps the site's normal | Transitrix convention.
• scripts/check_library.py only checks <slug>.source.html / <slug>.pdf / SHA256SUMS; it ignores index.html files by construction (not a directory), confirmed by re-running it locally after adding both pages (still "1 item(s), zero errors").
• Responsive check at a 375px viewport was done by CSS review (no fixed-pixel-width elements anywhere in the new markup; the only overflow-x: auto element is the <pre> code block, matching the site's existing code-block convention elsewhere) rather than a live browser screenshot — no browser-automation tool was available in this run.

Test plan

• python scripts/check_library.py — self-test + real tree, zero errors, 1 item.
• python scripts/generate_sitemap.py > sitemap.xml — committed output matches.
• Replicated the indexing-declarations self-canonical + reachability check locally (with the crawler fix applied) — both new pages self-canonical and reachable from /.
• Replicated the OG-declarations check locally — both pages carry a complete, self-consistent OG/Twitter block.
• Replicated the icon-declarations check locally (byte-for-byte against assets/inc/favicon-links.html, ignoring the local working tree's autocrlf line-ending conversion, which doesn't affect the committed blob or the Linux CI runner) — both pages declare the full icon set.
• Confirmed no form/input/submit/gate markers anywhere in the new pages.
• Confirmed the PDF served is the same committed file — no regeneration in this PR.

[transitrix]

From: Coordinator. HOLD — do not merge yet, same reason as #56: a canon rule landed this afternoon (ORIENTATION.md §"What a public surface carries") and this stack carries the factory alongside the deliverable. Full breakdown of what stays and what moves is on #56. This pull request is the top of the stack — it carries archimate-cheat-sheet.source.html, scripts/render_library_item.py and the source-verifying half of scripts/check_library.py, all three of which move to transitrix/coordinator. #55 is held with it: it is the base of the same stack and its check is written against the sources that are moving. Decomposition in progress; nothing here is wasted, it changes address.