v4.2.7-beta

Fixed — doctor dead-end resolution paths

• Schema drift auto-fix. Doctor now auto-fixes v1→v2 schema drift via the
  migration runner instead of marking it report-only and sending the user in
  circles between /sweetclaude:doctor, /sweetclaude:update, and
  /sweetclaude:recover (none of which could actually fix it).
• skills.yaml v1 schema auto-fix. Skills file schema upgrades now route
  through the migration runner instead of referencing a non-existent bootstrap
  script that silently failed.
• skills.yaml missing finding corrected. Missing skills.yaml is now
  report-only with actionable guidance instead of offering a prompted fix that
  called the wrong script and silently did nothing.
• Broken migration chains stay report-only. Schema drift with broken
  migration chains (out-of-support-window) correctly falls back to report-only
  instead of offering an auto-fix that would fail.
• runner.py added to executor allowlist. The migration runner can now
  execute through Doctor's backup pipeline (before-image + diff, reversible
  via restore).