docs(xl1-testing): correct local-chain cadence, producer wallet, and REST reads

[arietrouw]

Summary

Corrects skills/xl1-testing/local-chain.md against @xyo-network/xl1-cli 5.4.1 (bundled sources and live runs):

• Block cadence replaces "every few hundred ms". Plain xl1 start with no config file uses the CLI's dev preset (500 ms producer check, 5 s heartbeat, 200 ms finalizer check). A config file that lists the actors falls back to the schema defaults (10 s check, 5 min heartbeat, 500 ms finalizer check), so an idle chain sits at block 2 and a transaction lands in ~0–10 s. Adds the test polling budget and the rule that producer and finalizer heartbeats must match.
• Funding: the producer signs with the CLI's built-in development mnemonic (crane ribbon cook …, account 0 = 4e881c82…), not account 0 of test … junk; genesis still pays f39fd6e5…. --mnemonic replaces only the actor wallet; XL1_CHAIN__GENESIS_REWARD_ADDRESS moves the genesis funds.
• Benign log lines: findBestHead … (no mempool actor), Producer … has insufficient stake (redeclaration timer), and [shadow] … anchor-present (no EVM).
• REST readers: InPageGatewaysProvider transport="rest" needs a published-chain layout that plain xl1 start does not serve. Adds a recipe with @ariestools/aries-chain-serve, S3 publish bindings, publishOnFinalize, and mempool + indexer, and notes that the SimpleChainContractViewer pin fails with UnknownProviderError in 5.4.1.

Verification

• --dump-config for the no-config, config-file, --mnemonic, and genesis-address variants.
• Live chains on spare ports: dev preset (heartbeat every ~5 s, transfer finalized in 0.3 s); config-file actors (idle at block 2, transfers in 5–6 s); mempool added (no findBestHead); a 21-minute run (stake lines at 20 min); the REST recipe read back through getRestGateway; and the SimpleChainContractViewer pin (exit 70, UnknownProviderError).
• node scripts/validate-skills.mjs skills, the schema-literal tests, and rendered Claude/Codex previews.

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