Setting: roll child token usage into parent (recursive)

[XertroV]

Request

Add a setting that adds child subagent token usage into the parent’s usage totals.

Requirements

• Opt-in (or documented default — TBD, lean off so accounting stays as today unless enabled)
• Works recursively: depth 2+ agents roll up through each ancestor
• Cover components already tracked on lifetimeUsage: input, output, cacheWrite (cost only if/when we surface dollar cost)
• When enabled, parent-facing accounting (widget / notifications / session surfaces we own) reflects rolled-up totals
• Docs: clarify this is accounting visibility, not changing provider billing; child still runs its own session/API calls

Current behavior

Child usage stays only on the child AgentRecord. Nothing rolls into parent session stats. See src/usage.ts, AgentRecord.lifetimeUsage, manager onAssistantUsage.

Acceptance

• Setting in subagents.json + /agents → Settings (or equivalent)
• Recursive rollup on each child usage delta (or on child terminal + streaming option documented)
• Tests for depth 1 and depth 2+
• README / settings docs

Related

Local log: bugs.txt (setting: roll up child usage into parent)
Complementary (not the same): persist structured usage for extension consumers

[XertroV]

Implemented

• Setting rollupChildUsage (default off) in subagents.json + /agents → Settings → Roll up child usage
• Process-wide agent record registry (src/usage-registry.ts) so nested managers can walk parentAgentId
• On each assistant usage delta: add to the child, then roll the same delta into every ancestor (recursive)
• README documents accounting-only semantics (no change to provider billing)

Tests: test/usage-registry.test.ts, manager integration in test/agent-manager.test.ts, settings round-trip/apply.