vibe-qc 0.4.2 — Schrödinger's Llama (docs)

Documentation-only patch release. Five docs-side fixes that improve
the first-10-minutes user experience without touching any code:

  - Landing-page install snippet now uses the orchestrator
    (scripts/setup_native_deps.sh) instead of pre-orchestrator
    per-dep build commands.
  - 'Your first calculation' save-as-and-run guidance + quickstart
    'How to run the snippets' preamble.
  - New docs/running.md as the single source of truth for 'how to
    run vibe-qc' (script vs notebook vs CLI).
  - examples/README.md 'Running an example' section + 30 example
    Run: docstrings updated.
  - Landing page renders a 'Current release: X.Y.Z — codename' tip
    box. Codename catalogue (RELEASE_CODENAMES) added to
    docs/conf.py with v0.1.0=First Light, v0.4.0=Schrödinger's Llama,
    v0.5.0=Wilson's Otter; patch versions inherit their parent
    minor's codename.

CHANGELOG entries: see [0.4.2] block.

No library code changes. 879 tests / 25 skipped / 1 xfailed at
v0.4.1 baseline.