fix(tools): propagate tool registry to subagents (#1711)

* fix(tools): propagate tool registry to subagents via Clone

SubagentManager was created with an empty ToolRegistry and SetTools()
was never called, causing all subagent tool invocations to fail with
"tool not found". This was a regression from the multi-agent refactor.

Fix: clone the parent agent's tool registry into the subagent manager
after creation but before spawn/spawn_status registration — giving
subagents access to file, exec, web, and other tools while preventing
recursive subagent spawning.

- Add ToolRegistry.Clone() for independent shallow copies
- Call subagentManager.SetTools(agent.Tools.Clone()) in registerSharedTools
- Add tests for Clone isolation, empty clone, and hidden tool state

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(tools): fix cron_test build error and add TTL clone test

- Fix cron_test.go:229 — replace non-existent SubscribeOutbound(ctx)
  with select on OutboundChan(), matching the MessageBus channel API
- Add TestToolRegistry_Clone_PreservesTTLValue per reviewer feedback
- Add version reset note to Clone() doc comment

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

pkg/agent/loop.go

@@ -239,6 +239,11 @@ func registerSharedTools(
 		if (spawnEnabled || spawnStatusEnabled) && cfg.Tools.IsToolEnabled("subagent") {
 			subagentManager := tools.NewSubagentManager(provider, agent.Model, agent.Workspace)
 			subagentManager.SetLLMOptions(agent.MaxTokens, agent.Temperature)
+			// Clone the parent's tool registry so subagents can use all
+			// tools registered so far (file, web, etc.) but NOT spawn/
+			// spawn_status which are added below — preventing recursive
+			// subagent spawning.
+			subagentManager.SetTools(agent.Tools.Clone())
 			if spawnEnabled {
 				spawnTool := tools.NewSpawnTool(subagentManager)
 				currentAgentID := agentID