Workload: Failure and regression to GitHub issue automation

[dexcompiler]

Epic: #58

Type: Automation | Signal area: Reliability | Runtime mode: N/A

Deliver

Automation that turns scenario failures or threshold regressions into actionable GitHub issues: scenario name, seed, parameters, metrics, artifact links, reproduction steps.

Signals to capture

Every actionable failure becomes a triage-ready issue instead of a noisy log line.

Acceptance criteria

Failed nightlies (or designated workflow runs) create standardized issues automatically (template + labels + epic link where supported).