CI: watch UnityCLI and com.unity.pipeline releases, trigger reference update

[ArkTarusov]

Context. The command surface changes with UnityCLI and com.unity.pipeline releases; the reference in skills/unity-pipeline/references/editor-commands.md is pinned to specific versions (currently CLI 1.0.0-beta.3, pipeline 0.4.0-exp.1).

What to build. A scheduled GitHub Actions workflow that:

1. Polls https://packages.unity.com/com.unity.pipeline and compares the versions list against the version recorded in the reference preamble.
2. On a new pipeline version: runs the generator from command reference generator from package source — no editor, no dump #1 and opens a PR with the regenerated reference and its diff summary.
3. Checks for new UnityCLI binary releases and, on one, opens an issue to re-verify the CLI-level skill texts (flags, gotchas). The CLI has no known public release feed — the detection mechanism needs investigation first (unity upgrade check, docs changelog page, or the installer endpoint).

Depends on #1.