ETHERSCAN_MIGRATION.md: phased plan for true resolution time through the stack

Chain-sweep backfill (784k conds ≈ ~1k calls, not 8 days of per-cond
queries) → shadow audit → consumer flips shallowest-to-deepest →
trust.py simplification last. Ground rules codify the 2026-07-08
alignment-audit discipline: overlay never rewrite, one flip per day,
never coupled with follow-set changes, calibration continuity notes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

HANDOFF.md

@@ -42,11 +42,12 @@ The repo is authoritative; project memory has deeper history.
 
 ## Queued next-session work (in value order)
 
-1. **Exact-res_t migration**: `payouts.resolution_time(cond)` (Etherscan V2,
-   wired+verified 2026-07-08) gives true resolution timestamps; migrate
-   trust.py / validate_timing / portfolio.py to consume them instead of
-   endDate metadata. Alignment-grade change — same care as the 2026-07-08
-   audit. Backfill throttled ≤5 req/s (Etherscan free tier).
+1. **Exact-res_t migration**: plan agreed 2026-07-08 — execute
+   [ETHERSCAN_MIGRATION.md](ETHERSCAN_MIGRATION.md) phase by phase
+   (0: chain sweep backfill → 1: shadow audit → 2: validate_timing →
+   3: portfolio → 4: selection+floors → 5: trust simplification LAST).
+   One phase per session, before/after diffs, never coupled with
+   follow-set changes.
 2. **Empirical fill model**: every copy now logs a `book` snapshot (spread +
    5c depth) to the fills ledger; once a few weeks accumulate, fit slippage
    vs stake/depth and replace portfolio.py's flat SLIP haircut; add a depth