[Improve] Attribute inference usage to active workflows

[roomote-roomote]

​Opened on behalf of @mrubens. View the task or mention @roomote-roomote for follow-up asks.

What changed

• Annotate finalized primary-session inference usage with the active packaged workflow skill.
• Persist the workflow identifier in the existing inference usage details without changing the accounting schema or customer-visible transcript.
• Keep child and subagent inference usage untagged so it is not attributed to the parent workflow.

Why this change was made

Roomote already records per-message token usage and cost and separately tracks the active packaged workflow, but the two signals could not be correlated. Associating them makes workflow context and cost measurable using the existing accounting path.

Impact

There is no customer-facing behavior change. Operators can compare inference usage by workflow and identify expensive workflow context without a new cost calculator, database migration, or analytics subsystem.

[roomote-community]

1 issue outstanding. See task

• Preserve active workflow attribution after a harness reconnect (apps/worker/src/sandbox-server/lib/harnesses/opencode-server/harness.ts:5454).

_{Reviewed 2b62319}

[roomote-community]

ReconnectableHarness creates a fresh OpenCodeServerHarness with only initialSessionId after any disconnect, while activeWorkflowSkill is initialized to null and is not rehydrated. Once a workflow task reconnects, subsequent primary-session messages take this branch with no workflow skill and are persisted with details: null, losing the attribution this change is meant to preserve. Carry the active workflow through reconnect (or recover it from the session) and cover that path.