refactor: convert isinstance chains to match/case (part 3)

[EvanYao826]

Summary

#35902

Convert multi-branch isinstance/if-elif chains to structural pattern matching (match/case) for better readability and exhaustiveness checking.

Changes

8 files converted:

• trace-mlflow/mlflow_trace.py — trace dispatch (7 branches) + _parse_prompts (3 branches)
• trace-tencent/tencent_trace.py — trace dispatch (7 branches)
• core/tools/mcp_tool/tool.py — MCP content type dispatch with nested match (4 branches)
• advanced_chat/generate_task_pipeline.py — stream response dispatch (4 branches)
• workflow/generate_task_pipeline.py — stream response dispatch (4 branches)
• core/base/tts/app_generator_tts_publisher.py — message content type dispatch
• workflow_app_runner.py — graph event dispatch (10 branches)
• enterprise/enterprise_trace.py — trace dispatch (10 branches)

Benefits

1. Exhaustiveness checking — case _: pass makes it explicit when a type is unhandled
2. Better readability — structural pattern matching is cleaner than long if/elif chains
3. Missing branch detection — match/case makes it easier to spot missing type handling

[github-actions]

Pyrefly Type Coverage

Metric	Base	PR	Delta
Type coverage	0.00%	43.70%	+43.70%
Strict coverage	0.00%	43.22%	+43.22%
Typed symbols	0	22,131	+22,131
Untyped symbols	0	28,829	+28,829
Modules	0	2557	+2,557

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[asukaminato0721]

@dosu how is this pr

[dosubot]

This PR looks good. Here's a quick assessment:

✅ No issues detected. The conversion is safe and well-executed:

• Python version compatibility — Dify requires Python 3.12+ [1], so match/case (introduced in 3.10) is fully supported.
• Behavioral equivalence — The case ClassName() pattern is functionally identical to isinstance(obj, ClassName) for simple type dispatch. The PR correctly preserves nested isinstance checks within case bodies where more complex conditional logic is needed .
• Consistent conversion pattern — All 8 files follow the same mechanical 1:1 mapping (isinstance → case ClassName(), else → case _:), which reduces the risk of subtle bugs .
• Aligns with issue goals — This is part 3 of the systematic refactoring tracked in #35902, targeting files with long isinstance chains (7–11 branches) for maximum readability impact.

The refactoring improves readability and makes unhandled types explicit via case _: without changing any runtime behavior.

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