pub fn effective_policy(session: &Session) -> DerivePolicyExpand description
Resolve the effective derivation policy for session.
The persisted session policy is the baseline. Operators can override it process-wide via:
CODETETHER_CONTEXT_POLICY=legacyCODETETHER_CONTEXT_POLICY=resetCODETETHER_CONTEXT_RESET_THRESHOLD_TOKENS=<usize>
When there is no explicit override and the persisted policy is still
legacy, a recorded [CONTEXT RESET] marker auto-promotes the effective
policy to DerivePolicy::Reset so context_reset markers become live
immediately on the next turn.