* test(#3972): the guard fallback must share the opt-out ladder
* fix(#3972): one worktreesOptedOut ladder in planning-workspace, shared by resolver and guard
* test(#3972): without a workstream the root config is the effective config
* fix(#3972): guard the whole ladder body — malformed env values degrade, never throw
* chore(#3972): changeset fragment (pr number backfilled after PR creation)
* chore(#3972): backfill changeset PR number (3979)
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Co-authored-by: sim <sim@local>