chore(content): initial blog content (homepage blurb + 3 drafts)

[Skeyelab]

Adds homepage blurb and three engineering-focused draft posts under src/content/posts. These are drafts (frontmatter draft: true) and should not be auto-published. Do not merge until CI passes.

CI steps to verify:

• npm install
• npm test
• npm run build && npx linkinator ./public --failLevel error

Reviewers: @ericdahl-dev, design director
Labels: content, draft, do-not-merge/ci-failing

[Skeyelab]

CI analysis: build/test passed after link fix, but deploy step fails because the workflow needs the GITHUB_TOKEN to have id-token: write permissions (actions/deploy-pages calls OIDC). Please update repo settings or grant id-token permission in the workflow file. Temporary workaround: use peaceiris/actions-gh-pages with a PAT.

CI logs: Broken link -> fixed in commit 474218e (updated src/pages/index.astro). Build now succeeds. Deploy failed with error: "Ensure GITHUB_TOKEN has permission "id-token: write"."