vibe-qc 0.4.3 — Schrödinger's Llama (update workflow)

Documentation + ergonomics patch release. No code changes.

Adds a turnkey 'update existing checkout' workflow:

  - scripts/update.sh — one command replaces the four-step manual
    sequence (git fetch + checkout + pull → setup_native_deps.sh
    → pip install + verify). Handles branch/tag/remote-only refs
    uniformly, detects venvs at common paths, prints the new
    banner. --ref REF (default release), --rebuild-native-deps,
    --help.
  - docs/updating.md — user-facing reference covering both the
    easy button and the manual equivalent. Wired into the
    Getting started toctree between running and tour.

No library code changes. 879 tests / 25 skipped / 1 xfailed
at v0.4.2 baseline.