[umpireboulianne-design]

Summary

• Define the shared default timeout DEFAULT_RPC_TIMEOUT_MS = 10_000 (10 seconds), SubRosaRpcRequestTimeoutError, assertRpcTimeoutMs, withBoundedTimeout, and createBoundedFetch in packages/sdk/src/network.ts (re-exported from @sub-rosa/sdk).
• Wire DEFAULT_RPC_TIMEOUT_MS across SubRosaClient (rpcTimeoutMs), KeeperStatusClient (timeoutMs), createOzChannelsSubmitter (timeout), keeper CLI configuration (RPC_TIMEOUT_MS), createPaidFetch in services/appraisal-api/src/client.ts, and chainInfo / fetchRoundBeacon / fetchRoundSignature in packages/tlock/src/quicknet.ts.
• Document DEFAULT_RPC_TIMEOUT_MS (10_000 ms) in services/appraisal-api/README.md and add deterministic timeout unit tests across packages/sdk, services/keeper, services/appraisal-api, and packages/tlock.

Supply-chain review

• No package scripts or dependencies changed. If changed, explain why below.
• No .vscode/, workflow, or other editor/config file changes. If changed, list them below.
• No lockfile changes. If changed, explain the update below.
• No binary or font asset changes. If changed, list and justify them below.
• I confirm no automatic task (such as preinstall/postinstall) was added.
• I confirm no hidden executable payload (encoded blob, obfuscated command, or unexpected binary) was added.
• Any changed executable or binary was reviewed by a maintainer.

Testing

• node --import tsx/esm --test src/network.test.ts src/public-api-snapshot.test.ts in packages/sdk (17/17 tests pass)
• node --import tsx/esm --test src/dry-run.test.ts in services/keeper (passes)
• node --import tsx/esm --test src/quote-guard.test.ts in services/appraisal-api (15/15 tests pass)
• node --import tsx/esm --test src/quicknet.test.ts in packages/tlock (11/11 tests pass)
• node scripts/check-direct-time-access.mjs (passes)

Closes #534
Fixes #534