Wire dormant Orchestration 2.0 components into production flow

[Iron-Ham]

Summary

• File Conflict Prevention — Bridge claims file locks before instance creation and releases on all exit paths, preventing concurrent edits to the same files
• Context Propagation — Instances receive prior discoveries in their prompts and share completions for cross-instance awareness
• Mailbox Event Publishing — All inter-instance mailbox messages now publish MailboxMessageEvent to the event bus via WithBus functional option
• Adaptive Lead Observability — Scaling signal recommendations from the adaptive lead are logged in the pipeline executor
• Approval Auto-Approve — Bridge auto-approves gated tasks to prevent stuck states while preserving gate infrastructure for future interactive use
• Debate Protocol Integration — Pipeline review phase can identify conflicting task outcomes and record structured debate sessions for reviewer context

Details

Wires 6 dormant Orchestration 2.0 components into the production bridge/pipeline flow. These components were built as part of the Orchestration 2.0 meta-epic (#637/#638) but were never connected to the execution path.

File Lock Registry → Bridge: ClaimMultiple before instance creation, ReleaseAll on every exit path. File lock conflicts use gate.Release (not gate.Fail) to avoid burning retries when scaling increases concurrency.

Context Propagation → Bridge: GetContextForInstance injects prior discoveries into task prompts (filtered to MessageDiscovery + MessageWarning, capped at 50 messages). ShareDiscovery broadcasts completions on success paths.

Mailbox Event Publishing: WithBus functional option on NewMailbox; Hub passes its bus automatically. Nil bus is safe (no-op).

Adaptive Lead Signals: Executor subscribes to adaptive.scaling_signal events and logs them. Dispatch to goroutine prevents deadlock with the synchronous event bus.

Approval Gate: Auto-approve immediately after MarkRunning intercepts a gated task. TaskAwaitingApprovalEvent still fires for observability.

Debate Protocol: DebateCoordinator in pipeline/debate.go identifies file overlaps between completed tasks, creates structured debate sessions, and injects resolutions into the review team's LeadPrompt. Opt-in via WithDebate().

Test plan

• All existing tests pass with race detector: go test -race ./internal/bridge/... ./internal/mailbox/... ./internal/coordination/... ./internal/orchestrator/bridgewire/... ./internal/pipeline/... ./internal/team/...
• New debate_test.go covers conflict detection, debate resolution, and format functions
• New options_test.go covers WithBus event publishing, nil bus safety, backward compatibility
• Bridge E2E tests verify file locks are claimed/released during lifecycle
• gofmt, go vet, go build all pass