fix: add missing social-media preview image (og:image 404)

[raifdmueller]

Problem

The og:image and twitter:image meta tags in website/index.html point at og-image.png and twitter-card.png — but neither file existed (404 on the live site). Every share on LinkedIn, X, Slack, etc. rendered with no preview image.

Fix

• Add a 1200×630 branded preview card (dark theme matching the site, anchor mark, tagline "Shared vocabulary for precise communication with LLMs", "160+ curated anchors & contracts" pill, site URL).
• Ship it under both filenames the existing tags already expect (og-image.png, twitter-card.png) — no HTML change needed.
• Un-ignore the two PNGs in .gitignore (*.png is globally ignored with explicit ! exceptions, like logo.png/icon.png).
• Bump APP_VERSION to 0.8.2, add changelog entry.

The card was rendered from an HTML template via headless Chromium at exactly 1200×630.

Verification

• file confirms both PNGs are 1200 x 630.
• Meta tags unchanged and already reference the shipped filenames.

🤖 Generated with Claude Code

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yml

Review profile: CHILL

Plan: Pro

Run ID: 0ce6089c-970b-4d30-a52a-165865db6870

📥 Commits

Reviewing files that changed from the base of the PR and between 30bba04 and a3b67dd.

⛔ Files ignored due to path filters (2)

• website/public/og-image.png is excluded by !**/*.png
• website/public/twitter-card.png is excluded by !**/*.png

📒 Files selected for processing (3)

• .gitignore
• docs/changelog.adoc
• website/src/main.js

👮 Files not reviewed due to content moderation or server errors (3)

• .gitignore
• website/src/main.js
• docs/changelog.adoc

---

Warning

Walkthrough skipped

File diffs could not be summarized.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}