Add `wrap_with_deprecation_notice` helper in the subagent module that
merges a `_deprecation` block into a ToolResult's metadata. Applied
exclusively on alias invocations:
- `spawn_agent` → use `agent_spawn` (removed in v0.8.0)
- `delegate_to_agent` → use `agent_spawn` (removed in v0.8.0)
- `close_agent` → use `agent_cancel` (removed in v0.8.0)
- `send_input` → use `agent_send_input` (removed in v0.8.0)
Canonical names are unaffected. Each alias invocation also emits a
`tracing::warn` so the deprecation appears in audit logs. Documents
the deprecation schedule in `docs/TOOL_SURFACE.md`. Four unit tests
verify the notice shape and that canonical tools stay clean.
Refs #72
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Hunter Bown
c58d10ded1