refactor: move L1 network defaults source of truth to l1-contracts

[fcarreiro]

Summary

Prep for the foundation / node / fairies repo split: make l1-contracts own the canonical L1 contract configuration defaults instead of deriving them from spartan/environments/network-defaults.yml. The new source of truth is l1-contracts/scripts/network-defaults.json, published via @aztec/l1-artifacts and consumed directly by both the Solidity deploy scripts and @aztec/ethereum. This flips the dependency to spartan → l1-contracts, the right direction for the split.

Worth noting is that now the defaults in @aztec/ethereum read from the JSON in @aztec/l1-artifacts and NOT from the yml files. IIUC the yml files are for kubernetes deployment and this change would not affect someone that wants to run a docker image with a sequencer/prover.

Changes

• Add l1-contracts/scripts/network-defaults.json as the committed, canonical set of L1 contract defaults. This replaces the gitignored l1-contracts/generated/default.json that used to be generated from the yaml at bootstrap. It also adds the parameters RollupConfiguration.sol reads that were previously only defaulted in Solidity (AZTEC_SLASHING_QUORUM, AZTEC_ENTRY_QUEUE_*).
• Publish the JSON through @aztec/l1-artifacts (new package export + copied into the bundled foundry subtree by copy-foundry-artifacts.sh).
• @aztec/ethereum's config now imports the JSON from @aztec/l1-artifacts directly (import … with { type: 'json' }). Deleted the generated l1-contracts-defaults.ts and its generator (scripts/generate.sh), and dropped ethereum from the yarn-project bootstrap generate step.
• l1-contracts/scripts/load_network_defaults.sh now reads the JSON — network-agnostic, no network argument, no yaml. spartan's deploy_rollup_upgrade.sh switches to spartan's own network-aware yaml loader for its per-network needs.
• foundry.toml fs_permissions and the deploy .t.sol scripts read from scripts/network-defaults.json.
• The l1-contracts section of network-defaults.yml is now a hand-synced mirror of the JSON (it still feeds the slasher / cli generators and the networks presets). Docs updated: spartan/CLAUDE.md, the yaml header, and the governance rollup-upgrade tutorial.
• RollupConfiguration.sol now reads parameters via vm.envUint/envBool (required) instead of vm.envOr (silent Solidity fallback). Consequently the deploy-script tests (DeployAztecL1Contracts.t.sol, DeployRollupForUpgrade.t.sol) now forward those env vars from the JSON in setUp().

Behaviour change in l1-contracts tests

The tests now use the values in the network-agnostic JSON and therefore do NOT use the same values as before (devnet).

Testing

• l1-contracts: forge test passes for both deploy suites — DeployAztecL1ContractsTest::test_SmokeTest and DeployRollupForUpgradeTest::test_DeployThenUpgrade.
• @aztec/ethereum: builds cleanly; DefaultL1ContractsConfig loads from the JSON at runtime with exact bigint threshold values (no precision loss).

Closes https://linear.app/aztec-labs/issue/A-1358/decouple-spartan-network-configuration-and-l1-contracts

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 1 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033FLAKED\033 (8;;http://ci.aztec-labs.com/95ebff2feed46e35�95ebff2feed46e358;;�):  yarn-project/end-to-end/scripts/run_test.sh simple src/e2e_p2p/preferred_gossip_network.test.ts (199s) (code: 0) group:e2e-p2p-epoch-flakes