Remove anchor fragments from monitor-usage.md links (#4413)

Removed the `#token-usage-in-elastic-agent-builder` anchor from all
links to `monitor-usage.md` to simplify navigation and improve
maintainability.

**Changes:**
- Updated links in `chat.md`, `agent-builder-agents.md`, and `tools.md`
to reference `monitor-usage.md` directly without anchor fragments
- Links now point to the page itself rather than a specific section,
allowing the page structure to evolve independently

Before:
```markdown
[Token usage in Elastic Agent Builder](monitor-usage.md#token-usage-in-elastic-agent-builder)
```

After:
```markdown
[Token usage in Elastic Agent Builder](monitor-usage.md)
```

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solutions/search/agent-builder/agent-builder-agents.md

@@ -19,7 +19,7 @@ An agent parses user requests to define a goal and then runs tools in a loop to
 When you ask a question to an agent, it analyzes your request to define a specific goal. It selects the most appropriate tools and determines the right arguments to use. The agent evaluates the information returned after each action and decides whether to use additional tools or formulate a response. This iterative process of tool selection, execution, and analysis continues until the agent can provide a complete answer.
 
 :::{note}
-This iterative process consumes tokens. To understand how usage is calculated, refer to [Token usage in Elastic Agent Builder](monitor-usage.md#token-usage-in-elastic-agent-builder).
+This iterative process consumes tokens. To understand how usage is calculated, refer to [Token usage in Elastic Agent Builder](monitor-usage.md).
 :::
 
 {{agent-builder}} includes a default agent (named `Elastic AI Agent`) with access to all built-in tools. You can create specialized agents with custom instructions and selected tools to address specific use cases or workflows.

solutions/search/agent-builder/chat.md

@@ -36,7 +36,7 @@ This takes you to the chat GUI:
 Use the text input area to chat with an agent in real time. By default, you chat with the built-in Elastic AI Agent.
 
 :::{note}
-Conversations with agents consume tokens. To understand how usage is calculated, refer to [Token usage in Elastic Agent Builder](monitor-usage.md#token-usage-in-elastic-agent-builder).
+Conversations with agents consume tokens. To understand how usage is calculated, refer to [Token usage in Elastic Agent Builder](monitor-usage.md).
 :::
 
 :::{image} images/agent-builder-chat-input.png

solutions/search/agent-builder/tools.md

@@ -35,7 +35,7 @@ Tools enable agents to work with {{es}} data. When an agent receives a natural l
 Each tool is an atomic operation with a defined signature - accepting typed parameters and returning structured results in a format the agent can parse, transform, and incorporate into its response generation.
 
 :::{note}
-Tool execution and result processing consume tokens. To understand how usage is calculated, refer to [Token usage in Elastic Agent Builder](monitor-usage.md#token-usage-in-elastic-agent-builder).
+Tool execution and result processing consume tokens. To understand how usage is calculated, refer to [Token usage in Elastic Agent Builder](monitor-usage.md).
 :::
 
 ## Built-in tools