Add protocol-neutral cold-start sync (reactive feature)

[KaiCode2]

Summary

Adds a protocol-neutral cold-start sync mechanism to evm-fork-cache, gated under the existing reactive feature. A consumer declares the storage it needs warmed on startup and drives a bounded multi-round loop via a pure ColdStartPlanner — the driver owns all fetch/call IO, the planner owns all protocol decisions.

The headline win is a per-slot SlotFetch (Value / Zero / FetchFailed / NotAttempted) that closes the archive-miss gap: a fetch failure is now distinct from a genuine on-chain zero, which verify_slots could not express (it dropped per-slot Errs and kept only an aggregate count).

Base: this PR stacks on codex/reactive-reorg-recovery (the rev evm-amm-state pins). Motivating consumer: the AMM cold-start work in evm-amm-state (V3 slot0, V2 reserves, Balancer getPoolTokens access-list discovery) — adoption is a separate follow-up in that repo.

What's in it

A ColdStartPlan declares four independent, optional phases run in fixed order accounts → verify → probe → discover:

• verify — authoritative pinned re-fetch + dual-layer injection (inject_storage_batch_fresh), with a per-slot outcome.
• probe — classify at the pinned block without injecting (archive-miss check for slots you don't want to warm).
• accounts — ensure_account pre-seeding before discovery.
• discover — view-call access-list capture via call_raw_with_access_list, with an optional restrict_to filter.

A Done | Continue(next_plan) continuation drives data-dependent multi-round cold starts; ColdStartPin::Hash { require_canonical } pins a whole run to a hash and restores the prior block on every exit path.

New / changed

• src/cold_start/ (new, gated): ColdStartPlan/Call/Results/CallResult/RoundOutcome, ColdStartPlanner/Step, ColdStartConfig/Pin/RunReport/RoundSummary, ColdStartError, and EvmCache::{execute_cold_start_round, run_cold_start}.
• src/freshness.rs: SlotOutcome / SlotFetch (ungated, beside SlotChange).
• src/cache/mod.rs: verify_slots_core extraction (verify_slots / reconcile_slots behaviour unchanged), verify_slots_with_outcomes, ensure_account_blocking; classify + block_in_place_handle widened to pub(crate).
• tests/cold_start.rs (new): 19 offline acceptance tests; setup_cache_with_asserter added to tests/common.

Design notes

• Composition, not reinvention — every phase composes an existing primitive (verify_slots_inner, inject_storage_batch_fresh, call_raw_with_access_list, ensure_account, StorageBatchFetchFn); SlotChange and StorageAccessList are reused verbatim.
• No AMM concepts enter evm-fork-cache.
• Mid-round honesty — execute_cold_start_round returns RoundOutcome { results, error }, carrying partial results in the return type; on an accounts-phase hard error every unreached verify/probe slot is marked NotAttempted, the round is absorbed into the report, and on_results is skipped.
• Cold-start stays an EvmCache-level mechanism (no ReactiveRuntime coupling); require_canonical: true hash-pinning is its standalone reorg defense.

Validation (full release gate, all green)

cargo test · cargo test --no-default-features · cargo fmt --all --check · cargo clippy --all-targets --no-deps -- -D warnings · RUSTDOCFLAGS="-D warnings" cargo doc --no-deps (default + --no-default-features) · cargo +1.88.0 check --lib --locked · git diff --check. 19/19 cold-start tests pass; existing suite unaffected.

Not in scope (follow-up)

Consumer adoption in evm-amm-state (V2/V3/Balancer ColdStartPlanner impls, migrating its cold_start tests, bumping the pinned rev) — handoff doc to follow.

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