Add agent-friendly JSON workflow validation

[Austin243]

Summary

• add the versioned electrace.cli.v1 success/error envelope and opt-in --json output to every operational subcommand, including parse-time failures
• add strictly read-only electrace workflow validate MANIFEST --json with deterministic frame, command, input/output, dependency, scheduler, and warning resolution
• publish CLI/workflow-validation schemas and update the coding-agent guide and installable ElecTrace skill
• journal Slurm submissions safely so partial job IDs are structured, durable, and protected against blind or concurrent resubmission
• bump the pre-release package to 0.1.0a4 and require Typer 0.20+, the oldest validated CLI runtime

Compatibility

• plan, sampled volume, and workflow status retain their legacy raw JSON when --json is omitted
• explicit doctor --json and volume --json consumers now read the command payload under data; migration notes document the pre-release change
• help and version output remain human-readable

Validation

• 433 pytest tests
• Ruff lint and formatting
• strict mypy across 36 source files
• strict MkDocs build
• pre-commit hygiene/security hooks
• skill package validation and realistic forward-use test
• clean sdist/wheel build and fresh installed-wheel smoke on the minimum Typer 0.20 surface
• two independent adversarial reviews with clean merge verdicts