feat(core): update graph_mermaid.py

[chgjin]

This pull request includes a refinement to the _escape_node_label function in libs/core/langchain_core/runnables/graph_mermaid.py. The change improves the handling of special characters in Mermaid syntax by expanding the regex pattern to include additional characters.

Key change:

• libs/core/langchain_core/runnables/graph_mermaid.py: Updated the _escape_node_label function to use a more comprehensive regex pattern (mermaid_special_chars) for escaping special characters in Mermaid syntax. This ensures better compatibility and avoids issues with unsupported characters.Correct the _escape_node_label method to be compatible with multilingual title names

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1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
langchain	⬜️ Ignored	Preview		Aug 11, 2025 10:38pm

[codspeed-hq]

CodSpeed WallTime Performance Report

Merging #31577 will not alter performance

_{Comparing chgjin:patch-1 (1bb1095) with master (166c027)}

⚠️ Unknown Walltime execution environment detected

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For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

✅ 13 untouched benchmarks

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #31577 will not alter performance

_{Comparing chgjin:patch-1 (1bb1095) with master (166c027)}

Summary

✅ 14 untouched benchmarks

[mdrxy]

Would be worried about removing all non-alphanumerics (including Unicode) but since this is scoped to mermaid and private it LGTM. cc: @eyurtsev for final approval

[mdrxy]

@chgjin can you update test_graph_mermaid_escape_node_label to pass the test to reflect the new foo_bar? see this

[mdrxy]

@chgjin please update to resolve CI failures 🙏

[eyurtsev]

Will be resolved by this: #32857