🛡️ Sentinel: Add input validation for agent metadata extraction

[google-labs-jules]

🛡️ Sentinel: [security improvement]

Description

Added input validation for agent metadata extraction to prevent potential log injection or data pollution.

Vulnerability

Previously, agent_instance_id, parent_session_id, and parent_task_id were extracted from user prompts without validation. This could allow malicious actors to inject arbitrary strings (including path traversal characters or HTML/script tags) into the plugin's logs or metadata fields.

Impact

Medium/Low. While mostly leading to log pollution or potentially Stored XSS in log viewers (if vulnerable), it corrupted the integrity of the session metadata.

Fix

Implemented a strict isValidId check that only allows alphanumeric characters, hyphens, and underscores for extracted IDs. Malformed IDs are now ignored.

Verification

• Verified that malicious inputs like <script> or ../ are rejected using a test script.
• Verified that valid IDs are still extracted correctly.
• Ran full test suite (bun test).

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PR created automatically by Jules for task 16303121858403540985 started by @fpr1m3

[google-labs-jules]

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