gateway: phase-7 endpoints, run cap meters, tygo in CI

[Evanfeenstra]

Summary

Three stakgraph-only gaps from the gateway gap list, in one branch because they share the tygo-generated types.ts:

1. Cap meters on run detail (phase 9)

• The accumulator now stamps bifrost:meta:run:<id> per chain layer (max_cost_usd, max_steps, exp, parent; agent/user on the leaf) and indexes the leaf under bifrost:runs:user:<user> (ZSET scored by exp). Same TTL axis as cost:run; idempotent HSET on every call.
• GET /_plugin/runs/:id/state gains max_cost_usd / max_steps (null = no cap), exp, agent_name, user_id, and ancestors[] (nearest parent first, bounded walk, cycle-safe).
• RunDetail's live-state card draws a cost and a steps meter per budgeted run in the chain; a run at/over any cap (its own or an ancestor's) badges exceeded with a note about enforce_budgets.

2. Missing phase 7 endpoints

• /_plugin/spend/by-session, /_plugin/spend/by-model
• /_plugin/histogram/tokens, /_plugin/histogram/latency (nearest-rank p50/p95/p99 + sample count)
• /_plugin/sessions/:id, /_plugin/sessions/:id/summary — on metadata.session-id, not Bifrost's native session routes (those alias parent_request_id)
• /_plugin/users/:id/spend, /_plugin/users/:id/quota (Bifrost customer budget + in-flight runs from the new index; degrades cleanly without a Customer or without Redis)
• /_plugin/agents/:name/spend
• Window/bucket params now accept the full Bifrost duration vocabulary (1d, 1w, 1M, …), rolling from now; the SPA picker keeps its subset. Token totals are now filled in the existing rollups (they were left at 0).
• logstore_client_test.go added; handler tests for every new route. The e2e test against a real Bifrost is still not in CI (scripts/smoke-test.sh remains manual).

3. tygo in CI (phase 8 ship gate)

• types.ts is now genuinely generated (make tygo, byte-stable); the non-struct types moved to ui/src/api/manual.ts (unions, ApiError, trust mirrors, Bifrost chat/usage shapes).
• New .github/workflows/gateway-check.yml: go build/vet/test ./internal/..., make tygo-check with tygo pinned at v0.2.21, make ui-build.
• Supersedes Gateway: reconcile tygo codegen with SPA and enforce in CI #1563 (same approach, rebased onto current main and the new endpoints).

Docs: phase 7 inventory/vocabulary/checklist brought in line with the code; by-realm references dropped from phases 7/8; phase 9 tygo section updated; UI AGENTS.md updated.

Test plan

• go test ./internal/... green (auth: meta/index/lineage; adminapi: every new route, vocabulary, quota degradation, cap/ancestor state; logstore client)
• go vet ./internal/..., go build ./internal/...
• make tygo twice → identical output; tsc -b; vite build
• RunDetail verified in the Vite dev server against a mock /_plugin backend: chained meters (warning tones, capless steps, killed ancestor), capless fallback, over-cap badge + note
• Not verified against a real Bifrost + Redis stack (no compose run in this session)