feat: clone an agent hierarchy into another project

[antiv]

Narrowed 2026-08-06. The original scope (environment tags dev/staging/prod, promotion workflow with diff preview, promotion history, rollback of a promotion) assumes teams running several environments. MATE deployments run one instance, and the useful half — copying a working agent tree somewhere else — is nearly free given what already exists.

Problem

Reusing a configured agent hierarchy in another project means exporting JSON, hand-editing project ids, and importing — or rebuilding it in the dashboard.

What already exists

• GET /dashboard/api/agents/export and POST /dashboard/api/agents/import (shared/utils/dashboard/dashboard_server.py) already serialise and restore agent configs, including tools and relationships.
• agent_config_versions with rollback and version tags covers "undo a bad change" — the rollback half of the original promotion story.
• The template library (documents/TEMPLATE_LIBRARY.md) covers sharing a starting point across installations.
• WizardProvisioningService.promote_trial() already does a narrow form of promotion for wizard trials.

Scope

• "Clone to project" action on a root agent: deep-copies the agent and its sub-agents into a chosen target project, rewriting project_id and parent references.
• Name collision handling: suffix or prompt for a new root name.
• Optionally include the agent's memory blocks and file-search store assignments (checkbox).
• Audit entry for the clone.

Acceptance criteria

• Clone a root agent with its whole sub-agent tree into another project
• Cloned agents are immediately loadable (folders created as for a normal agent)
• Name collisions handled without corrupting the source
• Clone recorded in the audit log

Explicitly out of scope

Environment tags, diff-preview promotion workflow, promotion history table. Versioning already provides rollback, and single-instance deployments have nothing to promote between.