LEDGER-pov: refresh status notes for the completed proof; drop unused helper
The proof is complete, so the three historical "deferred/WIP/does-not-typecheck" status notes are replaced by one accurate note describing the module parameters (discharged downstream) and the four-summand accounting. Also refreshes the GOVS-coinFromGovDeposit and G₀/G' comments, the arithmetic-helpers prose, and removes the now-unused abcd-to-adcb shuffle. No proof changes (still --safe, EXIT 0). Co-Authored-By: Claude Opus 4.8 <[email protected]> Claude-Session: https://claude.ai/code/session_01We2YdXX2ozJAdAbCrRwi6r