🛡️ Sentinel: [CRITICAL] Fix command injection in text-to-speech

[omsingh02]

🚨 Severity: CRITICAL
💡 Vulnerability: Command injection risk when interpolating untrusted text directly into a subprocess.Popen PowerShell command using f-strings (e.g., f'$synth.Speak("{text}")'). If the input contains PowerShell metacharacters or quotes, arbitrary commands could be executed.
🎯 Impact: An attacker could execute arbitrary code on the host machine if they can control the text being spoken.
🔧 Fix: Avoid direct string interpolation with untrusted input in subprocess.Popen using powershell -Command. Instead, encode the payload using Base64 in Python (using utf-16le encoding to match PowerShell's [System.Text.Encoding]::Unicode) and decode it within the PowerShell script.
✅ Verification: Ran python -m compileall src/ to verify no syntax errors were introduced. Checked pytest src/ which passed (collected 0 items, meaning no test failures). Added an entry to .jules/sentinel.md to log the learning.

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PR created automatically by Jules for task 9911116812668969372 started by @omsingh02

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