[qduc]

What changes

Extract Term2's turn loop into the workspace package @qduc/agent-harness-core, with Term2 as its first consumer. A host supplies its model, tools, history and typed application context; it accepts events before the turn advances. Root and nested turns can set model- and tool-call caps, and compaction remains opt-in.

The dependency-free package is embedded in Term2's distribution. A packed-install test runs concurrent turns from a plain JavaScript consumer. Term2-specific policy and pricing stay in Session; the engine import guard has no remaining allowlisted edges.

Provider affinity, model factory state and OAuth account ownership are scoped to requests or application-owned instances. Refreshes are coordinated per account within one app, including cancellation, account removal and retry. Separate processes sharing a credential file still need external coordination.

Verification

• CI passed quality, static tests, integration, end-to-end, provider black-box and port checks on the current head, including the 14-hop message-path budget.
• Independent verification covered the packed package, concurrent contexts, nested authority, provider affinity and WebSocket dispatch, and OAuth account/refresh isolation.
• Local integration and end-to-end runs encountered environment limitations in nested shell execution and /proc PTY visibility; those tiers passed in CI.
• The design prerequisites are merged: Fix v2 parsing of native task tool tracking agent-runtime#2 and Upgrade Electron to a Node 24 runtime chat#39. ChatForge's Windows desktop package and real rendered UI were not tested as part of its prerequisite change.

Closes #224