Read exact execution-credit state

Reads the verified principal's organization-wide prepaid execution position from the authoritative PostgreSQL ledger. Desired and effective revisions remain distinct, and pending stays true until the control plane records PostgreSQL confirmation. Amounts are exact integer microdollars encoded as decimal strings; currency is USD and scale is six. Reserved credit has already been committed to a logical attempt but is not yet a settled debit. A missing hard cap means the customer elected no execution spending cap, never zero room. Shadow mode records what enforcement would have done without charging or blocking, and the activation boundary prevents retroactive charges.