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By: Codex <codex@openai.com>

Select analytic branches during master expression expansion

Expose condition-only branch probes in Rust and Python get_expression so dead analytic sectors are skipped before inlining. Keep formulas parametric and share the protected replacement semantics with select_branch. Preserve the upstream Symbolica migration.

Cover the reported massive C0, 256-bit and Python high-precision agreement, parameter retention, probe cache isolation, partial rules, and dead-definition pruning. Document the required branch_rules keyword and provide a runnable repo-API example.