fix(ai): address missing attributes and propagate agent name in AI integrations

[harryautomazione]

Description

This PR addresses several AI integration test failures reported in #5343 by fixing missing attributes, propagating the agent name, and structuring response text.

Fixes included:

1. Langchain: Added gen_ai.tool.type = "function" to on_tool_start in sentry_sdk/integrations/langchain.py to fix missing tool description assertions.
2. Agent Name Propagation:
   • Introduced a shared context stack in sentry_sdk/ai/utils.py.
   • Updated langgraph.py to manage agent name scope during invoke/ainvoke.
   • Updated openai.py to inherit gen_ai.agent.name from the stack on generated span details.
3. PydanticAI:
   • Refactored string format wrapper output extraction inside pydantic_ai/spans/invoke_agent.py to construct structured message models when feasible, aligning behavior accurately with multi-turn trace assertions.

Issues

• resolves: ❌ AI Integration Tests Failed #5343

Reminders

• PR title uses conventional commit style (fix:, feat:)

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

📋 Changelog Preview

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Entries from this PR are highlighted with a left border (blockquote style).

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New Features ✨

• (asgi) Add option to disable suppressing chained exceptions by alexander-alderman-webb in #5714
• (logging) Separate ignore lists for events/breadcrumbs and sentry logs by sl0thentr0py in #5698

Bug Fixes 🐛

Anthropic

• Set exception info on streaming span when applicable by alexander-alderman-webb in #5683
• Patch AsyncStream.close() and AsyncMessageStream.close() to finish spans by alexander-alderman-webb in #5675
• Patch Stream.close() and MessageStream.close() to finish spans by alexander-alderman-webb in #5674

Other

• (ai) Address missing attributes and propagate agent name in AI integrations by harryautomazione in #5727

Documentation 📚

• Add note on AI PRs to CONTRIBUTING.md by sentrivana in #5696

Internal Changes 🔧

• Add -latest alias for each integration test suite by sentrivana in #5706
• Use date-based branch names for toxgen PRs by sentrivana in #5704
• 🤖 Update test matrix with new releases (03/19) by github-actions in #5703
• Add client report tests for span streaming by sentrivana in #5677

Other

• Update CHANGELOG.md by sentrivana in #5685

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