feat(at): add persistent maps and cross-AT reads

[QuickMythril]

Summary

Adds consensus-backed persistent key/value maps for ATs, with synchronous cross-AT reads (including same-block earlier writers). This is the storage foundation for the SMPL faucet's exact deduplication.

• Opcodes: map GET 0x0600 / SET 0x0601; contracts write only their own map, may read any AT's map.
• Consensus safety: map writes live in a Block-owned overlay during validation (candidate validation never writes the database); they commit atomically with AT state during block processing and reverse on orphan via rollback journals.
• Verifiability: every AT state now commits a canonical hash of its current map contents (canonical signed-key ordering), so a node's serving table is directly checkable against consensus state.
• Pricing: creating a live entry costs 100 steps via the AT library's new platform pricing hook; reads/overwrites/deletes/no-ops/cap-rejected writes stay at the normal 10-step cost. Step cost comes from the Java default, not shipped JSON, so the live Previewnet config hash is unchanged (regression-tested: 8e655fc30e325d11ec44d350dd456ad80bff0a507935133edc3db5345e9253e5).
• Caps & governance: 500-entry per-AT ceiling, ratcheting (dev-group governance may only raise it); chain-parameter API surface included.
• Activation: Previewnet block 70,000; mainnet disabled.
• Schema: repository advances to version 3 (current map rows, rollback journals, nullable map roots on AT states).

Dependency provenance

Pins com.github.QortiumDev:AT:33df17d (adds the pricing hook and fixes an unenforced platform-function precheck — see QortiumDev/AT#9, which must merge as a merge commit first so the pin stays canonical). Vendored artifact:

• jar SHA-256 2f40ee7acfdeaa1dfc35615a6ba7870dcc4e85977d3e9e3a1b7ad6bcef340f3b
• pom SHA-256 43f6ac5cfae6cf0f823f972c929b3d3844493cf1e510268c8369c31275eb8b4d

Design doc: docs/chain-design/at-map-storage.md. Changelog entry included.

Verification

• AT library: 179/179 tests.
• Core focused map/config/repository/API set: 124 tests, including exact block-70,000 boundary, same-block cross-AT reads, orphan rollback, cap ratcheting, candidate-validation-must-not-write coverage, and live config-hash preservation.
• Core full clean suite: mvn -B clean test -DskipTests=false — 2,675 tests, 0 failures, 0 errors (64 expected skips).

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