chore: trim README for clarity and structure

[EleanorWho]

What does this PR do?

Trim README for clarity and structure

• Add table of contents
• Fix heading hierarchy (H3 → H2 throughout)
• Merge related sections (Documentation + Client SDKs → Resources; Community + Star History + Contributors)
• Fold one-line installer into Overview, remove redundant Benefits sub-section
• Tighten prose throughout

Improves AgentReady Concise Documentation score from 69 to 85/100 (Threshold: ≥75)

[leseb]

Thanks! While we are it, can you:

• remove the Post Training column from the API / Providers table?
• remove the Builtin distribution
• Remove the diagram since it's not representing the state of the stack today

If others agree, i'd even remove the API Providers & Distributions since the doc has an equivalent, (i think/hope).

Thanks!

[EleanorWho]

@leseb Done with the first 3 suggestions. And I agree with the tables of Distributions because the doc contains more detailed information. But I'm not sure about the API Providers table since it's more intuitive to scan for information. However, I also think this table is too large to read.

What about regroup it into something like:

  ┌───────────┬───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
  │    API    │                                                       Providers                                                       │
  ├───────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ Inference │ OpenAI, Anthropic, Gemini, Ollama, vLLM, Fireworks, Together, Groq, AWS Bedrock, SambaNova, Cerebras, WatsonX, TGI,   │
  │           │ NVIDIA NIM/NEMO                                                                                                       │
  ├───────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │  Agents   │ Fireworks, Together, PyTorch ExecuTorch                                                                               │
  ├───────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ VectorIO  │ ChromaDB, Milvus, Qdrant, Weaviate, SQLite-vec, PG Vector, Infinispan, NVIDIA NEMO                                    │
  ├───────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │  Safety   │ SambaNova, AWS Bedrock, Together, NVIDIA NIM                                                                          │
  ├───────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │   Eval    │ NVIDIA NEMO, NVIDIA                                                                                                   │
  ├───────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ DatasetIO │ HuggingFace, NVIDIA NEMO, NVIDIA                                                                                      │
  └───────────┴───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

[leseb]

@franciscojavierarceo @mattf @cdoern how do you feel about removing API Providers & Distributions section since it's not well maintained and our doc has all of it covered (and it's auto-generated)?

[leseb]

@franciscojavierarceo @mattf @cdoern how do you feel about removing API Providers & Distributions section since it's not well maintained and our doc has all of it covered (and it's auto-generated)?

let's revisit later, not urgent.