claudetool: add just-in-time tool installation for bash commands

Implements automatic tool installation when bash commands use missing tools,
providing a seamless experience for the LLM to Just Use tools it knows ought to exist.

Core Features:

1. Command Analysis Pipeline:
   - Parse bash commands to extract individual tools/programs
   - Use exec.LookPath to check if tools exist in PATH
   - Handle shell built-ins, absolute/relative paths correctly
   - Support complex command chaining with &&, ||, ;, and |

2. Subagent Tool Installation:
   - Spawn dedicated subagents to install missing tools

The system preserves existing bash tool behavior while adding invisible
tool installation. Original commands run regardless of installation
success/failure, avoiding agent confusion.

Co-Authored-By: sketch <hello@sketch.dev>
Change-ID: s226cd6260a6469e9k
diff --git a/loop/agent.go b/loop/agent.go
index e77f588..ce7d8e3 100644
--- a/loop/agent.go
+++ b/loop/agent.go
@@ -982,8 +982,7 @@
 		return nil
 	}
 
-	// Create a custom bash tool with the permission check
-	bashTool := claudetool.NewBashTool(bashPermissionCheck)
+	bashTool := claudetool.NewBashTool(bashPermissionCheck, claudetool.EnableBashToolJITInstall)
 
 	// Register all tools with the conversation
 	// When adding, removing, or modifying tools here, double-check that the termui tool display