[feat] Add a minimal command-only workflow runtime #1076

Parent: #818

Goal

Deliver the smallest real workflow vertical slice: pull validates command-only workflows independently, start creates durable state, and the local driver completes a run through the same next and report operations exposed to external drivers.

Scope

• Add the initial workflows/*.yaml v1alpha1 subset: required header, ordered steps, unique IDs, one command per step, and optional shorthand output.
• Validate each workflow file independently during pull and push, with file, line, and field diagnostics.
• Cache only validated workflow definitions. If a previously valid file becomes invalid, retain its last valid cached version; a newly invalid file has no runnable version.
• Continue syncing all other workflows and resources when one workflow is invalid.
• Add only teamai workflow start, next, and report.
• Use the common { "data": ... } / { "error": ... } envelope.
• Persist minimal run, revision, attempt, lease, step-state, and outcome data using atomic writes and a per-run lock.
• Reject stale, repeated, wrong-attempt, and wrong-driver reports.
• Implement a local command driver using the same engine operations.
• Support success, failed, and released.

Out of scope

Agent steps, retry, cancel, control flow, worktrees, gates, records, publish/resume, and external drivers.

Dependencies

• Blocked by: none
• Unblocks: [feat] Run prompt and agent steps with the local driver #1077, [feat] Add DAG conditions and composable sub-workflows #1078, [feat] Publish privacy-preserving workflow run records and stats #1083

Acceptance criteria

• A two-command workflow completes through the real CLI.
• State survives process exit between next and report.
• Concurrent callers cannot lease the same step.
• One invalid workflow does not block other resources or valid workflows.
• Its last valid version remains runnable; the invalid revision never becomes runnable.
• Diagnostics identify the file and source location.

Verification

Focused validation, cache, locking, transition, and stale-report tests; build/typecheck/lint; one real-CLI command-workflow E2E. Regenerate commands.md and add both workflow guide languages.