Doc: miscellaneous (#10641)

### What problem does this PR solve?

### Type of change

- [x] Documentation Update

docs/guides/agent/agent_component_reference/indexer.md

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+---
+sidebar_position: 40
+slug: /indexer_component
+---
+
+# Indexer component
+
+A component that defines how chunks are indexed.
+
+---
+
+An **Indexer** component indexes chunks and configures their storage formats in the document engine.
+
+## Scenario
+
+An **Indexer** component is the mandatory ending component for all ingestion pipelines.
+
+## Configurations
+
+### Search method
+
+This setting configures how chunks are stored in the document engine: as full-text, embeddings, or both.
+
+### Filename embedding weight
+
+This setting defines the filename's contribution to the final embedding, which is a weighted combination of both the chunk content and the filename. Essentially, a higher value gives the filename more influence in the final *composite* embedding.
+
+- 0.1: Filename contributes 10% (chunk content 90%)
+- 0.5 (maximum): Filename contributes 50% (chunk content 90%)