🔒 [Security] Fix command injection in PowerShell notification

[Tcode-Motion]

🎯 What: Fixed a command injection vulnerability in stdlib/src/notification.rs where user-provided notification title and body variables were passed insecurely to a PowerShell subprocess on Windows.
⚠️ Risk: If an attacker could control the notification title or body (e.g., via a TechScript string generated from unvalidated external input), they could potentially execute arbitrary PowerShell commands on the host machine.
🛡️ Solution: The solution entirely bypasses PowerShell's parsing and escaping quirks by Base64-encoding the strings in Rust (base64::prelude::BASE64_STANDARD.encode). The PowerShell script itself was rewritten to decode these Base64 strings dynamically at runtime, ensuring that malicious payloads cannot break out of the string context. The TS_NOTIFY_TITLE and TS_NOTIFY_BODY environment variables were also removed to prevent accidental leakage. The -NoProfile flag was added to ensure isolated and rapid script execution.

---

PR created automatically by Jules for task 14505776625068902587 started by @Tcode-Motion

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.