docs: fix broken links and syntax in examples

[LGmatrix13]

Description

• Fix incorrect links.
• Fix examples where TinyAgent.create includes a name of a agent framework like google or openai.
• Fix examples to provide the model provider for model_id in AgentConfig.
• Fix typo in docs/serving about A2A.

PR Type

• Documentation

Checklist

• I understand the code I am submitting.
• I have added unit tests that prove my fix/feature works.
• I have run this code locally and verified it fixes the issue.
• New and existing tests pass locally.
• Documentation was updated where necessary.
• I have read and followed the contribution guidelines.
• AI Usage:
  • No AI was used.
  • AI was used for drafting/refactoring.
  • This is fully AI-generated.

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