Drops the "workflow-step" MockSessionPurpose enum value and the
workflowStepId / workflowStepTemplateId plumbing through
agent-runtime, agent-session-helpers, mock-provider, executor, and
merger. The seeded-workflow-prompts script loses its FN-5205
rationale comment + test (no longer applicable now that workflow
steps run through the regular session purposes).
Also strips the stale FN-5482 architecture-invariant bullet from
AGENTS.md and the corresponding audit-event line from
docs/architecture.md (the self-healing reclaim invariant they
described no longer holds).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
