Fix: Correct pagination and early termination bugs in chunk_list() (#11692)

## Summary

This PR fixes two critical bugs in `chunk_list()` method that prevent
processing large documents (>128 chunks) in GraphRAG and
  other workflows.

  ## Bugs Fixed

  ### Bug 1: Incorrect pagination offset calculation
  **Location:** `rag/nlp/search.py` lines 530-531

**Problem:** The loop variable `p` was used directly as offset, causing
incorrect pagination:
  ```python
  # BEFORE (BUGGY):
  for p in range(offset, max_count, bs):  # p = 0, 128, 256, 384...
es_res = self.dataStore.search(..., p, bs, ...) # p used as offset

  Fix: Use page number multiplied by batch size:
  # AFTER (FIXED):
  for page_num, p in enumerate(range(offset, max_count, bs)):
      es_res = self.dataStore.search(..., page_num * bs, bs, ...)

  Bug 2: Premature loop termination

  Location: rag/nlp/search.py lines 538-539

Problem: Loop terminates when any page returns fewer than 128 chunks,
even when thousands more remain:
  # BEFORE (BUGGY):
if len(dict_chunks.values()) < bs: # Breaks at 126 chunks even if 3,000+
remain
      break

  Fix: Only terminate when zero chunks returned:
  # AFTER (FIXED):
  if len(dict_chunks.values()) == 0:
      break

  Enhancement: Add max_count parameter to GraphRAG

  Location: graphrag/general/index.py line 60

Added max_count=10000 parameter to chunk loading for both LightRAG and
General GraphRAG paths to ensure all chunks are
  processed.

  Testing

  Validated with a 314-page legal document containing 3,207 chunks:

  Before fixes:
  - Only 2-126 chunks processed
  - GraphRAG generated 25 nodes, 8 edges

  After fixes:
  - All 3,209 chunks processed ✅
  - GraphRAG processing complete dataset

  Impact

These bugs affect any workflow using chunk_list() with large documents,
particularly:
  - GraphRAG knowledge graph generation
  - RAPTOR hierarchical summarization
  - Document processing pipelines with >128 chunks

  Related Issue

  Fixes #11687

  Checklist

  - Code follows project style guidelines
  - Tested with large documents (3,207+ chunks)
  - Both bugs validated by Dosu bot in issue #11687
  - No breaking changes to API

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

rag/nlp/search.py

@@ -537,7 +537,8 @@ class Dealer:
                 doc["id"] = id
             if dict_chunks:
                 res.extend(dict_chunks.values())
-            if len(dict_chunks.values()) < bs:
+            # FIX: Solo terminar si no hay chunks, no si hay menos de bs
+            if len(dict_chunks.values()) == 0:
                 break
         return res