v0.6.0 — real per-token cost metering + per-run budgets

Added

• Real per-token model-call metering. The Anthropic proxy now parses
  upstream token usage and stamps model, usage, and a real per-token
  costUsd onto the execution audit row — non-streaming JSON is buffered and
  parsed; SSE responses are tee()'d so the client streams token-by-token
  uninterrupted while a background consumer reads usage off the second branch.
  A self-contained pricing table (src/pricing/) computes cost (cache-tier
  aware) and refreshes daily from LiteLLM's community JSON. Closes the gap where
  proxied model calls contributed $0 to budgets.
• Per-run budgets. A new scope: run budget caps a single agentic run
  (all calls sharing actor.runId) by USD, tokens, and/or call count — the unit
  where recursive/agentic burn compounds. Denies RUN_BUDGET_EXCEEDED at the
  action boundary via the existing allow/approve/deny + signed-approval
  machinery; the Anthropic proxy enforces it before the costly model call.
  An actor may now carry both an actor-scoped guardrail and a per-run cap (all
  matching rules are enforced). Ships disabled (observe-first).
• Run correlation (runId) threaded end-to-end: x-runestone-run-id on the
  proxy, runId on the TypeScript client, and GATEKEEPER_RUN_ID for the MCP
  server and Claude Code hook (hook falls back to the session id). For callers
  that can't set headers (e.g. the Claude Agent SDK, which only exposes
  ANTHROPIC_BASE_URL), the proxy also recovers the run id from an
  …/anthropic/_run/<runId> base-URL prefix.
• /usage and budget aggregation now expose real summed totalCostUsd /
  totalTokens per bucket and support a runId filter (jsonl + Postgres sinks).

Changed

• audit_logs gains model / usage / cost_usd columns (drizzle migration
  0003). drizzle.config.ts now targets the schema files directly so
  db:generate works (the barrel's ESM .js re-export broke drizzle-kit's
  loader). AuditEntry, logToolExecution, UsageRow, UsageFilter, and
  BudgetRule gain optional fields; all changes are backward compatible.