Sayay-007 companion: recognize sayay.check spans in the metrics pipeline.

- cost/metrics.ts: new counter qhaway_sayay_decisions_total{action,user}
  (allow/warn/degrade/block) derived from tool_name=sayay.check spans
- dashboard: add 'Budget Guardrails (Sayay)' barchart panel
- tests: metric emission test + dashboard panel count 7→8 (total 141/141)
- version 0.11.0