Reuse go-livepeer activity tracking for local payment recipient checks #35

Problem

Challenge creation and payment receipt each resolve BondingManager and call isActiveTranscoder, contributing four synchronous RPC calls per paid request at the baseline in builder-core #89. See PaymentChain.IsActiveAt.

go-livepeer uses OrchestratorWatcher to maintain activation/deactivation information, then orchestrator.isActive checks the local database against the cached initialized round. Adapt this existing mechanism to node, reusing only the storage/watcher pieces needed for payment admission.

Work and acceptance

• Make warm challenge and receipt activity checks local. Initialize missing state through bounded work and update it from activation/deactivation and round events. Handle missed events, removed logs/reorgs, and BondingManager address changes through the shared observer/binding infrastructure.
• Keep the explicit ticket recipient distinct from the orchestrator's signing/node address. Check the recipient's activity at the same observation used for the payment's other chain checks; do not mix a newer activity/round result with older payer funds.
• Retain useful additions from BlueClawNetwork/livepeer-node PR #1: observe the configured recipient during initialization, isolate an entry failure from unrelated entries, pin cold reads to the observation block, and apply freshness/refusal rules to paid readiness. Its full ChainView implementation need not be imported to obtain those properties.
• Test warm challenges and receipts without recipient-activity RPCs, active/inactive and future activation/deactivation rounds, a recipient distinct from the node key, round rollover, reorgs, contract replacement, and unavailable/stale state. Unknown or unverifiable state must not authorize paid work. Readiness and payment admission should use the same state.

Uses shared block/round state #31 and retained contract bindings #32.

Reuse and attribution

Incorporate existing go-livepeer code and relevant tests as much as possible. Inspect originating git history; preserve original authorship and git-level provenance with suitable cherry-pick -x commits or a history-preserving import where practical. Where adaptation prevents that, retain license/copyright notices and add inline attribution naming the source repository, file, commit, and author(s). Preserve equivalent attribution for any code or tests taken from PR #1.