fix(diagnostics): separate whole-run budget

[rldyourmnd]

Summary

• add an explicit five-minute diagnostic exporter run budget
• preserve the twenty-second per-S3-request timeout
• require the run budget to remain below the ten-minute service deadline
• bump the strict exporter config schema

Natural incident

A burst of 24+ real diagnostic bundles exhausted the former derived 60-second budget. Four timer runs failed during source rescan before the backlog recovered; the corrected one-minute alert paged the incident.

Validation

• focused exporter config/runtime tests
• make verify

Closes #187.