fix(cli): accept auto/mps devices in pixelrag index build

[codysj]

Summary

pixelrag index build --device only accepts cpu/cuda, but the rest of the
stack supports auto/mps too: build() routes device in ("cpu","mps","auto")
to the local embedder, and embed_cpu declares choices=["auto","cpu","mps","cuda"].
So --device auto (the smart default) and --device mps fail at argparse with
"invalid choice" even though they'd work.

Config (device: auto in pixelrag.yaml) is unaffected, this only fixes the CLI
override flag, which currently can't express the values the config can.

Changes

• Widen --device choices to auto, cpu, mps, cuda to match build()/embed_cpu.
• Add a CLI smoke test asserting the rendered choices token.

Testing

• uvx ruff check . / uvx ruff format --check .
• uv run pytest tests/test_cli.py -v

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[andylizf]

Thanks — the --device choices fix is correct and needed (auto/mps work downstream but argparse rejects them).

However, this PR is based on an older main and its diff reverts 10+ recently-merged PRs (~680 lines of unrelated regressions: removes --cdp-url, --user-data-dir isolation, pre-commit hooks, non-numeric ID fix, agent timeouts, version bump, etc.).

Could you rebase onto the latest origin/main? The fix itself is just pipelines.py (the choices line) + the new test — everything else should drop away after rebase.

git fetch upstream main
git rebase upstream/main
git push --force-with-lease

[codysj]

Rebased onto latest main, diff is now just the --device choices line + the CLI test. Thanks for the catch!