Completes the vars round-trip: pull now fetches the app's OWN env-agnostic
vars (`vars_list` filtered to scope `*`, non-tombstone) and writes them
into the manifest `[vars]` block, alongside scripts/routes/secrets.
Inherited group vars stay out (pull exports own rows only, §4.6); a value
TOML can't represent (e.g. JSON null) is skipped with a warning. So
`pic pull` → edit → `pic apply` is now lossless for app config vars.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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