feat(aztec.js): expose #[abi] globals on generated contract classes

[vezenovm]

Resolves UX improvements as part of resolving #21761

Stacked on #25184. Generated contract classes now expose #[abi(tag)] globals as decoded values, grouped by tag.

Before (runtime accessor over kind-tagged AbiValues):

import { getGlobalsByTag } from '@aztec/aztec.js';

const { EXPORTED_LIMIT_CONSTANT } = getGlobalsByTag(TestContract.artifact, 'limits');
// { kind: 'integer', sign: false, value: '00...0064' }

After (baked into the generated class, fully typed):

TestContract.globals.limits.EXPORTED_LIMIT_CONSTANT; // 100n
TestContract.globals.constants.EXPORTED_STRING_CONSTANT; // "exported"

Also versions the codegen cache so generator changes regenerate wrappers whose artifact hashes are unchanged.

• Adds cache tests covering cache hits, missing generated outputs, and generator-version invalidation.

Audit fixes

Resolves AztecProtocol/barretenberg-claude#4481
Resolves AztecProtocol/barretenberg-claude#4479

• A user global exported under the reserved #[abi(storage)] tag is rejected with a clear error instead of crashing
• Absent tags named after Object.prototype members (toString, __proto__, etc.) return {} as documented instead of throwing.
• The artifact schema no longer drops __proto__ record keys (zod's record parser skipped them)
• Two storage layouts declaring the same contract_name (a dependency contract sharing the root contract's unqualified name) raise an explicit ambiguity error instead of the first one silently supplying the layout.
• Reading globals from a pre-cutover artifact reports that the artifact predates named globals and must be recompiled. This is a mitigation for AztecProtocol/barretenberg-claude#4474; general cutover enforcement is tracked in F-848.