Add CI-ready tx-path integration suite and CI/Makefile wiring

[BioMark3r]

Motivation

• Provide an end-to-end, CI-capable tx-path integration that verifies basic transaction flows (send wei, deploy contract, submit raw signed tx) and exercises the new UI token gate (X-TX-TOKEN) when available.
• Keep tests self-contained for CI: avoid external services, implement retries/timeouts to reduce flakiness, and allow clean skipping when required secrets or optional components are not present.

Description

• Add scripts/tests/tx_integration.sh, a strict-mode bash script that boots or reuses a devnet, waits for RPC readiness, discovers chain id, resolves a sender key (SENDER_PRIVATE_KEY → FAUCET_PRIVATE_KEY → dev-only .data discovery), and runs three tx checks (send 1 wei to burn address, deploy minimal test contract, submit explicit raw signed tx) with receipt polling and assertion logic.
• Implement reusable helpers in the script: rpc_call, rpc_get_result, wait_for_receipt, get_nonce, get_gas_price, estimate_gas, local signing via a temporary Node+ethers workspace, and UI vs raw-RPC mode selection with clear failure when TX_HTTP_URL is set but TX_TOKEN is missing.
• Wire into build and CI: add test-tx and test-all Makefile targets and make make test optionally include tx tests when CI_TX=1, and update scripts/ci/run.sh to run the tx suite when CI_TX=1.
• Update GitHub Actions CI job to set CI_TX=1 and expose optional secrets placeholders (SENDER_PRIVATE_KEY, FAUCET_PRIVATE_KEY, TX_HTTP_URL, TX_TOKEN) without hardcoding values, and document usage and skip/fail behavior in README.md.

Testing

• bash -n scripts/tests/tx_integration.sh (syntax check) succeeded.
• make test-tx was exercised in this environment but failed during the repo build step due to inability to fetch/build polygon-edge (external GitHub clone failed with CONNECT tunnel failed, response 403), which is an external network issue unrelated to the new tx test logic.
• The new script contains timeouts, retries, and receipt-waiting logic and was exercised up to devnet build invocation during local validation; when run in a CI environment with network access and provided key secrets the suite is expected to perform all three tx checks end-to-end.

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Codex Task