* fix(agents): clear legacy auto fallback pins
* fix(agents): repair legacy auto-fallback test mock and tighten review feedback
Add hasLegacyAutoFallbackWithoutOrigin to the live-model-switch agent-scope mock so the agents-core lane runs, simplify the redundant hasSessionModelOverride guard, use a single source of truth for the legacy-pin staleness check with a comment on the load-bearing modelKey guard, and add preservation/edge-case/guard regression coverage. Rename the misleading primary-probe agent test.
* style(agents): format rebased fallback fix
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Co-authored-by: Peter Steinberger <steipete@gmail.com>
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