fix(bb-sol): run forge tests with pinned solc

[AztecBot]

Summary

• Fixes the latest PR feat: merge-train/spartan-v5 #24053 dequeue cause after test(prover-node): make checkpoint store pruning test deterministic #24130: merge-group run 27623199860 failed in x2-full because forge test --no-match-contract Base attempted to resolve https://binaries.soliditylang.org/linux-amd64/list.json and hit a DNS failure.
• Makes barretenberg/sol bootstrap export the pinned l1-contracts/solc-0.8.30 path for forge commands.
• Makes the generated bb-sol CI test command download the pinned solc via l1-contracts/bootstrap.sh download_solc, then run forge with FOUNDRY_SOLC=../../l1-contracts/solc-0.8.30 and --offline.

Verification

• git diff --check
• ./bootstrap.sh ci attempted from repo root; this branch has no ci command (Unknown command: ci).
• ./bootstrap.sh ci-full-no-test-cache attempted to match the failed merge-queue shard; local container stopped before bb-sol because .claude/tests/agents_symlink_test fails in this workspace and the test engine exits early.
• ./bootstrap.sh in barretenberg/sol passed, generating VKs and compiling with Solc 0.8.30 offline.
• FOUNDRY_SOLC=../../l1-contracts/solc-0.8.30 forge test --offline --no-match-contract Base passed: 168 tests, 0 failed.

---

Created by claudebox · group: slackbot