test(templates): render every template with satori

[prakashNalla]

Description

Adds tests/templates/render.test.ts, which runs Satori at 1200x630 on every template from getAllTemplates(): once with its defaults, and once with every non-required text/textarea field set to ''. The 8 fonts are read from public/fonts with fs, so it doesn't go through og-engine.ts or font-loader.ts. Test names include the template id. Also updated the line in CONTRIBUTING.md that said the tests don't run Satori yet.

Closes #78

How I Tested This

• npm run check (0 errors, 0 warnings) and npm run test (21 files / 470 tests pass) on Node v22.23.3
• The new file is 220 tests (110 templates, 2 cases each) and takes about 1.5s.
• Removed display: 'flex' from the outer multi-child div in blog/minimal-dark.ts (not committed): both blog-minimal-dark cases fail with Expected <div> to have explicit "display: flex" or "display: none" if it has more than one child node. Put it back and they pass.

AI Assistance

Claude helped me write the tests.

Type of Change

• Tests
• Documentation

Screenshots

N/A, tests and one line of docs.

Checklist

• This PR targets dev
• I was assigned the linked issue
• npm run check passes
• npm run test passes
• For a bug fix: the new test fails without my change
• Tested locally with npm run dev
• Screenshots included for visual changes
• New templates follow the Template Guidelines

[anurag629]

Thanks @prakashNalla, nice one. I ran it on top of dev: all 220 renders take about a second, and taking display: 'flex' off the outer div in blog/minimal-dark.ts fails both of its cases with the Satori error, same as you said. npm run check and all 470 tests pass. Merging.