fix(ci): add CNAME file to docs/ and fix mkdocs deployment (#23)

**Problem:**
- GitHub Pages custom domain kept getting reset
- Workflow used `mkdocs gh-deploy --custom-domain mnemex.dev` flag
- This flag doesn't exist, causing deployments to fail
- Failed deployments left GitHub Pages API without custom domain set

**Solution:**
- Add CNAME file to docs/ directory (standard mkdocs pattern)
- Remove invalid `--custom-domain` flag from workflow
- MkDocs automatically deploys CNAME file to gh-pages branch
- GitHub Pages API setting manually configured via `gh api` command

**How it works:**
- CNAME file in docs/ is copied during `mkdocs gh-deploy`
- Both CNAME file AND GitHub Pages API must be set
- This ensures custom domain persists across deployments

Fixes the recurring issue of custom domain being reset.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: prefrontalsys

.github/workflows/docs.yml

@@ -46,5 +46,5 @@ jobs:
         run: mkdocs build --strict
 
       - name: Deploy to GitHub Pages
-        # Include custom domain to preserve CNAME on each deploy
-        run: mkdocs gh-deploy --force --custom-domain mnemex.dev
+        # CNAME file in docs/ dir will be deployed automatically
+        run: mkdocs gh-deploy --force

docs/CNAME

@@ -0,0 +1 @@
+mnemex.dev