Studio Code: Tighten tool payload guards for truncated assistant calls

[youknowriad]

Summary

• Move payload-guard checks to tool execution so each tool call can be validated against its own call ID
• Block wpcom_request when the assistant response was truncated and the tool arguments may be incomplete
• Keep payload-size guidance in tool descriptions and raise the model output cap for PI sessions
• Expand coverage for remote WordPress.com request truncation and the updated token limit

Testing

• Updated unit coverage for payload-safety guidance and truncated wpcom_request handling
• Not run (not requested)

[wpmobilebot]

📊 Performance Test Results

Comparing 0051082 vs trunk

app-size

Metric	trunk	0051082	Diff	Change
App Size (Mac)	1339.26 MB	1339.26 MB	+0.01 MB	⚪ 0.0%

site-editor

Metric	trunk	0051082	Diff	Change
load	1800 ms	1720 ms	80 ms	🟢 -4.4%

site-startup

Metric	trunk	0051082	Diff	Change
siteCreation	9626 ms	9613 ms	13 ms	⚪ 0.0%
siteStartup	4917 ms	4920 ms	+3 ms	⚪ 0.0%

---

Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)