fix(workflow): align MCP tool template behavior

[FinleyGe]

Summary

• preserve MCP child tool description as the preview node intro when adding an MCP tool
• prevent MCP toolsets from being dragged directly from the node template list, matching system toolset behavior
• avoid duplicate getSystemToolTemplates requests when opening system toolsets by letting the system-tools effect own those loads

Tests

• git diff --check
• git diff --check HEAD~1..HEAD
• not run: local Vitest/tsc are unavailable because this worktree does not have completed node_modules; corepack pnpm exec reports Command not found for vitest and tsc

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	18.07%	1598 / 8839
🔵	Statements	18.09%	1680 / 9285
🔵	Functions	15.99%	337 / 2107
🔵	Branches	15.08%	762 / 5050

File Coverage

No changed files found.

Generated in workflow #1354 for commit 309e29f by the Vitest Coverage Report Action

[github-actions]

✅ Admin Preview Image Ready!

ghcr.io/labring/fastgpt-pr:admin_309e29fed8f115f434e319fcfa758cee54e85a56

🕒 Time: 2026-07-09 17:02:10 (UTC+8)

[github-actions]

✅ Build Successful - Preview fastgpt Image for this PR:

ghcr.io/labring/fastgpt-pr:fastgpt_309e29fed8f115f434e319fcfa758cee54e85a56

🕒 Time: 2026-07-09 17:01:26 (UTC+8)