AD-501: Define Runtime Adapter Interface

[alph-cmky]

Source: docs/development/task-backlog.md

Milestone: Phase 5: Runtime Adapters and Task Execution

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AD-501: Define Runtime Adapter Interface

Goal: Decouple task orchestration from specific CLIs.

Files:

• Create packages/runtime-adapters/src/execution/runtime-adapter.ts
• Create packages/runtime-adapters/src/execution/task-events.ts
• Create tests for adapter contracts

Tasks:

• Define adapter capabilities for executeTask, cancelTask, and getCapabilities.
• Define streamed task events for stdout, stderr, tool events, diff, completion, and failure.
• Commit with message feat: define runtime adapter interface.

Acceptance Criteria:

• Codex, Claude, and shell execution can share one orchestration interface.