Teams cost

[Felixoid]

Summary

Adds token usage and cost tracking for child Pi processes launched by agent_team. Each message_end RPC record carries the child's AssistantMessage.usage payload; RpcUsageTracker (in rpc-message-end-handler.ts) accumulates it synchronously as steps run. On step completion the cost flows into StepState, surfaces as StepSnapshot.usage (per-step) and RunSnapshot.teamUsage (run total), and appears in run_status/step_result model output.

In interactive Pi, a separate footer status line (team: $X.XXX ↑Xk ↓Xk ...) accumulates across all agent_team runs in the session via ctx.ui.setStatus. This is distinct from the parent session's own $X.XXX cost counter and is controlled by the new agent_team:footer-cost boolean flag (default true).

Scope

Proposal issue, if required:

Checklist

• This branch is based on current origin/main. It based on Fix gate tests for npm --json output format change from array to object #16
• The PR is scoped to one coherent change.
• I did not bump package.json version.
• I did not create a dated release section in CHANGELOG.md.
• User-visible unreleased changes are recorded under ## Unreleased, if applicable.
• I did not reintroduce removed compatibility paths, old action names, stale trust gates, or non-enforced authority paperwork.
• I did not weaken role capability truth: package:validator requires effective bash; package:worker requires effective edit or write.
• I did not run npm publish, create tags, push release branches, or create GitHub Releases.

Design-gate check

This PR changes any of the following:

• public agent_team actions or schema
• graph authority, tool/capability policy, or package-agent semantics
• persistence, recovery, reattach, cleanup, or retention
• mutation/edit behavior, git worktrees, or patch handling
• scheduling/background/repeated execution
• provider/model/extension discovery policy
• secret, credential, environment, or filesystem trust boundaries

No design-gate boxes apply. teamUsage and usage are additive read-only fields on existing snapshot types; no action schemas, authority gates, or persistence paths change. Here's the proposal issue #15

Validation

Paste fresh command output or explain why a command is deferred.

pnpm run typecheck
pnpm test
pnpm run gate
git diff --check

They pass clean, but don't fit the limit.

$ tsc --noEmit
$ node --import ./tests/node-test-ref-timers.mjs --no-warnings --experimental-strip-types --loader ./tests/pi-peer-loader.mjs --test tests/*.test.ts
....
ℹ tests 269
ℹ suites 0
ℹ pass 269
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 11290.306636
$ pnpm run typecheck && pnpm test && pnpm run smoke:fake-pi && pnpm run check:pack && pnpm run check:pi-load && pnpm run check:public-docs && pnpm run check:source-size
$ tsc --noEmit
$ node --import ./tests/node-test-ref-timers.mjs --no-warnings --experimental-strip-types --loader ./tests/pi-peer-loader.mjs --test tests/*.test.ts
.....
ℹ tests 269
ℹ suites 0
ℹ pass 269
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 11634.507153
$ node --no-warnings --experimental-strip-types --loader ./tests/pi-peer-loader.mjs tests/smoke-fake-pi.ts
$ node --experimental-strip-types tests/check-pack.ts
$ node --no-warnings --experimental-strip-types --loader ./tests/pi-peer-loader.mjs tests/check-package-load.ts
$ node --experimental-strip-types tests/check-public-docs.ts
$ node --experimental-strip-types tests/check-source-size.ts
Time: 41.92 s.

Notes for reviewers

• Cost source: usage is accumulated from message_end RPC records (AssistantMessage.usage), not from a get_session_stats fetch. This avoids any async race between a stats request and natural child close. If a step produces no message_end records with usage (e.g. fake child in tests), usage stays undefined and no footer write occurs.
• Partial cost on failure/cancel/timeout: RpcUsageTracker captures all message_end events received before termination; partial cost is preserved.
• Footer state: sessionTeamUsage and countedRunsBySession are in-memory maps in the extension closure, cleared on session_shutdown. The status line is only written when a run terminates with real usage, and only cleared on shutdown if cost was ever accumulated.
• Flag: agent_team:footer-cost false disables the footer line going forward; it does not retroactively clear an already-set status.
• rendering.test.ts: the setStatus guard now scans src/ (implementation files must not touch UI) plus a positive assertion that any setStatus in index.ts must use FOOTER_COST_FLAG.
• check-source-size.ts: two files exceeded the 18432-byte budget after additions; extracted RpcUsageTracker into rpc-message-end-handler.ts and token/cost formatters into result-model-text.ts.