refactor: remove in-product Relay orchestration

[rynfar]

Retires Pylon's bridge to the Relay Orchestrator Claude plugin. It was a stand-in while upstream's orchestrator was unavailable; upstream shipped orchestrator v2 (de34391427), so this removes the bridge rather than carrying two delegation implementations.

Removed

• orchestration/RelayWorkerBridge.ts (1858 lines) and orchestration/RelayCli.ts — plugin discovery via installed_plugins.json and scripts/relay.mjs
• provider/relayMcpConfig.ts — PYLON_RELAY_CLI opt-in and Codex app-server args
• Optional-service wiring in server.ts, ws.ts, OrchestrationReactor, ProviderRuntimeIngestion
• Relay MCP injection in ClaudeAdapter and CodexAdapter
• The Relay Orchestrator section of docs/user/thread-sidebar.md

Wire contract

Drops the relay-only fields source: "relay", relaySequence, relayPriorUsage.

cancellable and watchable stay — they are generic capability flags that Prime and native agents also use, with !== false defaults.

No data migration: these were all Schema.optional, and Schema.Struct ignores excess properties on decode, so events persisted before this change still decode. A new subagentRuntime test folds a legacy relay-shaped payload and asserts it becomes an ordinary agent row.

Migration 063_ClearUnprojectedRelayOutages is kept — it is registered at index 63 and already applied, so it stays immutable.

Logic that collapsed

• ProjectionSnapshotQuery — removed the relay_lifecycle / active_relay_lifecycle CTEs and their pinned-activity union
• ThreadBackgroundLiveness — dropped the relay set. No work outlives its session now, so clearThreadLiveness deletes the thread entry outright and hasNativeBackgroundWork is a size check
• subagentRuntime — deleted the attempt/sequence fence (acceptRelayEvent), per-attempt reset, cumulative usage accounting and the now-dead addUsage; canCancelSessionAgent lost its third detachedControlsAvailable parameter
• ChatView.logic — planBackgroundAgentStop reduced algebraically to canInterruptParent with no detached workers, so it is deleted and ChatView uses a plain canStopBackgroundWork
• web session-logic + mobile threadActivity — removed the relay.binding/relay.activation skips, the origin-backfill, the resulting dead toolOrigins maps, and relay-panel: spawn-group keys

Out of scope

The managed relay tunnels are a different subsystem from June 2026 and are untouched: packages/shared/src/relay*, packages/contracts/src/relay*, packages/client-runtime/src/relay/, apps/server/src/relay/, infra/relay/, deploy-relay.yml, and the relay:read/relay:write scopes.

Pair mode needed no work here — it was already removed by eb73be4a27 (#673) on 2026-09-19.

Verification

• Typecheck clean: t3, @t3tools/contracts, @t3tools/client-runtime, @t3tools/web, @t3tools/mobile (run per package; vp run -F/--filter silently skipped some)
• vp test run green on the changed scope: 12 files, ~560 tests, including ThreadBackgroundLiveness, ProjectionSnapshotQuery, subagentRuntime, session-logic, AgentsPanel, threadActivity, sessionAgentMenu, both adapters, and migration 063
• Lint clean on changed files (0 errors; remaining ChatView.tsx warnings are pre-existing)
• ClaudeAdapter.test.ts fails if CLAUDE_CODE_ENABLE_TODO_TOOLS is set in the ambient environment — pre-existing, unrelated; 192/192 pass with it unset

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	14.0 KiB	14.0 KiB	+14 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.3 KiB	7.3 KiB	+5 B (+0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.7 KiB	6.7 KiB	+9 B (+0.1%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.0 KiB	58.0 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	9	9	0 (0.0%)	21	✅
Claude	Total thread wire	14.0 KiB	14.0 KiB	+9 B (+0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.3 KiB	7.3 KiB	+2 B (+0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.7 KiB	6.7 KiB	+7 B (+0.1%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.9 KiB	58.9 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: ea2f22f · PR result: abed954 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 115.8 KiB
• Claude decoded thread snapshot: 116.4 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.