fix: make malformed tool call arguments trigger retry instead of agent exit

[hyknerf]

Summary

Fixes intermittent agent exit when MiniMax (or other providers) send malformed tool call arguments.

Problem

When a model sends invalid JSON in tool call arguments, the agent would exit prematurely instead of retrying the request. This was reported in issue #2641 where MiniMax M2.7 would occasionally exit with "Finished" after a tool call instead of continuing with the tool result.

Root Cause

ToolCallFull::try_from_parts() was using ToolCallArguments::from_json() which silently stores invalid JSON as Unparsed. This meant malformed arguments weren't being detected, leading to silent failures.

Solution

1. Added ToolCallArguments::parse_json() - Properly parses JSON strings with error handling, attempting serde_json first then falling back to json_repair for recovery

2. Updated try_from_parts() to use parse_json() - Parse failures now return Retryable errors that trigger automatic retries

3. Added Error::tool_call_json_error() helper - Creates properly wrapped Retryable errors for malformed JSON

Testing

• All existing tests pass (586 in forge_domain, 661 in forge_app)
• Added test test_into_full_with_tool_call_parse_failure_creates_retryable_error to verify retryable error behavior

Closes #2641

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[autofix-ci]

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[amitksingh1490]

@hyknerf could you please allow maintainers to push autofix is not able to push the changes