Phase A4 slice 1: adopt evm-fork-cache cold-start (V2/V3 planners)

[KaiCode2]

Summary

Adopts the new protocol-neutral evm_fork_cache::cold_start mechanism. Replaces the imperative AmmAdapter::cold_start with a per-adapter ColdStartPlanner driven by EvmCache::run_cold_start, and replaces the cached_storage(..).is_none() proxy with the upstream per-slot SlotFetch classification (the archive-miss fix). V2/V3 only this slice — Balancer V2 (discover→verify) is slice 2; the reactive RepairAction::ColdStart executor is slice 3.

⚠️ Two merge caveats

1. Interim dependency pin. evm-fork-cache is bumped from 27ae8762 to the cold-start-sync branch tip 903af3d (= 27ae8762 + the additive cold-start module), because evm-fork-cache#12 is not yet merged. The bump is purely additive. Re-pin to the main merge commit before merging this to evm-amm-state main.
2. Stacked on #8. This branches off the A8 tip because it ports A8's *_strict_* / missing_liquidity cold-start tests. The diff shows A8 + slice-1 until Phase A8 (slice): adapter test-matrix hardening #8 merges — merge Phase A8 (slice): adapter test-matrix hardening #8 first.

What changed

New src/adapters/cold_start.rs (always-on — cold_start rides the default-on reactive feature we already depend on):

• AdapterColdStartPlanner — upstream initial_plan/on_results + a finish hook mapping accumulated state + run report → ColdStartOutcome (mutating pool metadata/status).
• private Bridge newtype forwarding to evm_fork_cache::cold_start::ColdStartPlanner (no trait-upcasting).
• AdapterRegistry::cold_start(&mut PoolRegistration, &mut EvmCache, ColdStartPolicy) -> Result<ColdStartOutcome, ColdStartError> — resolves the adapter, drives the bounded loop, finalizes. Missing adapter / unsupported → Ok(Unsupported); an upstream ColdStartError propagates as Err.

Trait (traits.rs): cold_start → cold_start_planner(&self, &PoolRegistration, ColdStartPolicy) -> Result<Box<dyn AdapterColdStartPlanner>, UnsupportedReason>.

V2 planner (single verify-only round): reproduces the prior end-state (slots 6/7/8, metadata merge preserving config fee_bps, Lazy/HotSlotsOnly), sourcing the reserves verdict from SlotFetch. Key improvement — a genuine on-chain Zero (degenerate → PurgeSlots) and a FetchFailed archive miss (→ VerifySlots) now produce distinct repairs.

V3 planner (multi-round): the prior current-tick-word warm-up re-expressed as data-dependent Continue rounds (slot0+liquidity → current-tick bitmap word → that word's initialized tick {0,3} slots); HotSlotsOnly stops after round 1, Lazy defers the word, a cold/unfetchable slot0 → NeedsRepair. The multi-word adaptive scan stays deferred (future Continue rounds — no upstream change needed). Config V3 metadata preserved.

Tests

• New manager-authored tests/cold_start_adoption.rs (6 acceptance tests: the Zero-vs-FetchFailed distinction, Lazy==Eager invariant, V3 ready/missing-layout/failed-slot0).
• The 14 existing trait-level cold-start tests in tests/adapter_reactive.rs ported to registry.cold_start(..), assertions' intent preserved (incl. the warm→ExactFromInput-no-resync synergy).
• The 2 non-address-keyed cases in tests/adapter_a1.rs adapted to assert cold_start_planner(..) returns Err(Custom) (MockCache can't drive the EvmCache loop).
• Spec: docs/phase-a4-slice1-spec.md.

Validation

Full CI matrix green locally: fmt; clippy default + adapters-only + no-default (-D warnings); cargo test default (109+22+4+28+6) + adapters-only + no-default; cargo doc -D warnings. The cold-start path compiles in the adapters-only (heavy-dep-free) build.

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