Restore lightrag-hku 1.4.x compatibility and drop hardcoded 1536-dim embeddings

[mmavka]

Trying to run knowledge-mcp 0.4.2 against the latest lightrag-hku (1.4.16) with a local Ollama setup hit three errors in a row. This PR fixes all of them.

What's broken

1. llm_model_max_token_size removed in lightrag-hku 1.4.x

LightRAG.__init__() no longer accepts llm_model_max_token_size. Creating a KB fails with:

TypeError: LightRAG.__init__() got an unexpected keyword argument 'llm_model_max_token_size'

Dropped the kwarg from the constructor call in rag.py. The behaviour it used to control is now handled elsewhere in lightrag-hku and doesn't need to be set explicitly here.

2. Several QueryParam fields removed in lightrag-hku 1.4.x

The per-KB config template populates QueryParam with ids, model_func, chunk_top_k, and enable_rerank. None of those exist in the current QueryParam dataclass, so any query crashes with:

TypeError: QueryParam.__init__() got an unexpected keyword argument 'ids'

(or one of the other three, depending on dict iteration order).

Filtered those four keys out of final_query_params before the QueryParam construction. The existing description filter right above is doing the same dance, so I slotted the rest in next to it.

This is the conservative fix: the per-KB config can keep emitting those fields without breaking, and if any come back upstream we don't have to touch anything else.

3. openai_embed is hardcoded to 1536 dims

openai_embedding_func in openai_func.py delegates to lightrag.llm.openai.openai_embed, which is wrapped with @wrap_embedding_func_with_attrs(embedding_dim=1536) (i.e. OpenAI text-embedding-3-* dimensions baked in via decorator).

Fine for OpenAI, but anyone pointing the embedding endpoint at an OpenAI-compatible server with a different model (Ollama bge-m3 at 1024 dims, mxbai-embed-large also 1024, etc.) gets:

total elements (1024) cannot be evenly divided by expected dimension (1536)

embedding_dim is already configurable in config.yaml (lightrag.embedding.embedding_dim), but never honoured because the decorator on openai_embed overrides it.

Rewrote the inner function to call the OpenAI-compatible endpoint directly with AsyncOpenAI instead of going through openai_embed. Six lines, respects whatever dimension the endpoint actually returns. The EmbeddingFunc wrapper just below (lines 90–93) still reads embedding_dim from config, so dimensions are validated correctly downstream; they're just no longer pinned to 1536 in the inner function.

How tested

Local setup:

• knowledge-mcp 0.4.2 with these patches
• lightrag-hku 1.4.16
• OpenAI-compatible LLM endpoint (small Go proxy fronting OpenRouter, gpt-oss-120b free)
• Ollama serving bge-m3 (1024-dim) at http://localhost:11434/v1

After the patches:

• create <kb> and add_text <kb> <file> succeed; entity/relation extraction runs cleanly through OpenRouter
• Queries via the MCP tools (answer, query_hybrid, query_local, query_global, retrieve) all return synthesised answers with citations
• KB persists across server restarts

Before the patches each of the three issues blocks at a different stage (create / first query / first embedding call).

Notes

• Didn't touch the LightRAG dependency in pyproject.toml. Pinning to a known-good range would be more solid long-term, but it's outside what I needed today.
• There's a cosmetic RuntimeError: no running event loop at shell exit. Unrelated, doesn't affect ingest or query results. Can look at it separately if useful.
• The QueryParam kwarg filter is the minimal one: only keys I actually saw blowing up. There may be more dead fields in the default per-KB config; happy to do a follow-up sweep if you want.

Let me know if you'd rather split this into separate commits (compat fixes vs the embed change). They're independent, and I can rebase.