chore(ci): delete jekyll-gh-pages.yml — no Jekyll site here (#57)

## Summary

Doomed-CI cleanup. \`jekyll-gh-pages.yml\` exists in this repo but there
is no \`_config.yml\` at root and \`gh api repos/.../pages\` returns
404. Estate language policy bans Jekyll outright in favour of
\`hyperpolymath/casket-ssg\`. Every trigger fails at the Jekyll-build
step.

Keeping \`codeql.yml\` in place — the doomed-CI audit found a vendored
\`.js\` file at \`examples/javascript/nop.js\`, which is enough for
CodeQL to produce results (LIKELY_OK_VENDORED rather than DOOMED). Can
be revisited if results are noisy.

## Audit context

Identified by an estate-wide doomed-CI audit on 2026-05-27 (Track A —
Jekyll workflow on non-Pages repo).

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

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath