fix: agent security and linting improvements

[Piyush0049]

Description

This PR introduces critical fixes for agent stability and defense in depth security, alongside resolving native Windows linting warnings.

Key Changes

• RAG Goroutine Leak: Added a cancellable child context and synchronization channel to the RAG ToolSet. This ensures the forwardEvents and StartFileWatcher goroutines are cleanly terminated when Stop() is called, preventing silent memory and file descriptor leaks across tool reloads.
• Execve Environment Truncation: Added \x00 validation to static environment variables in script_shell.go. This prevents malicious or malformed config.yaml files from injecting NUL bytes that would silently truncate the process environment at the kernel execve boundary.
• Linting Cleanups: Resolved native errorlint, noctx, and bodyclose warnings in Windows specific files (using errors.As, context.Background(), and explicit body closure) and safely managed gosec directives to ensure a perfectly clean golangci-lint run state.

Testing Instructions

• Verified golangci-lint run reports 0 issues.
• Verified task test passes successfully.

[aheritier]

Same here @Piyush0049

Please provide more details about the issue you are trying to solve. Is it something which happens often? What are the symptoms?

Right now the PR doesn't provide enough context to understand if you are fixing a bug or if these are just code reviews by an LLM which could easily hallucinate bugs.

Thanks