fix: sanitize tool_use.id on session resume to prevent 400 error

[UmmeHabiba1312]

Description

This PR fixes the "Invalid tool_use.id format" 400 Bad Request error that occurs when resuming a session using --resume or continue_conversation.

Root Cause

When resuming a previous session, the SDK loads the full conversation history, which may contain tool_use.id values that do not follow the strict format required by the Claude API / CLI (toolu_[a-zA-Z0-9_-]+).
These malformed IDs (e.g., plain UUIDs, numeric strings, or IDs with invalid characters) cause the backend to reject the request with a 400 error.

Solution

• Added a new utility function sanitize_tool_use_ids() in src/claude_agent_sdk/_utils.py.
• This function ensures every tool_use.id and corresponding tool_result.tool_use_id follows the correct format by:
  • Adding the required toolu_ prefix if missing.
  • Replacing any invalid characters with underscores.
• Applied the sanitization in two places for maximum coverage:
  • In SubprocessCLITransport.connect() for initial resumed history.
  • In SubprocessCLITransport.write() for any subsequent streamed messages containing tool blocks.

This change is non-destructive, safe, and only modifies IDs when they are invalid.

Testing

• Verified that sessions with previously invalid tool_use.id values now resume successfully without 400 errors.
• Existing functionality (new sessions, normal tool use) remains unaffected.

Checklist

• Added sanitize_tool_use_ids() helper
• Updated subprocess_cli.py to apply sanitization on resume paths
• Updated CHANGELOG.md under Unreleased section
• Code passes linting and import tests

Related Issue

• Fixes Invalid tool_use.id format during session resume causes API 400 error #856