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

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). That can
be revisited later if the JS results turn out to be noisy.

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

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

Author: hyperpolymath