v2.17.3

Changed

• Adopt the per-package ~/.scitex/writer/containers/<tool>.sif convention
  for SIF paths (#117). Configs, shell modules, installation scripts, and
  Makefile now point at the canonical per-package containers root (operator
  design 8566 + sac PR #293). command_switching.src extracts a shared
  _writer_resolve_sif(tool, var) helper that resolves canonical first,
  falls back to the legacy ./.cache/containers/<tool>_container.sif with a
  [DEPRECATED] log line on hit (keeps pre-migration caches working until
  rebuilt via scitex-writer containers install <tool>). The canonical
  ~/.scitex/writer/containers/texlive.sif artifact built earlier today is
  picked up immediately on upgrade — no rebuild required for texlive.
  Mermaid / tectonic / imagemagick still need their builds in a separate
  follow-up (P1.b of the brand-wide ecosystem containers/bin migration).
• 4-way duplication across setup_latex_container,
  setup_tectonic_container, setup_mermaid_container,
  setup_imagemagick_container collapsed via the shared resolver helper:
  command_switching.src 528 → 507 lines.