Remove LangChain4jMcpServerDefinition substitution when Camel drops HttpMcpTransport usage

`camel-langchain4j-agent` still references `dev.langchain4j.mcp.client.transport.http.HttpMcpTransport` for the deprecated `sse` MCP transport type. That class was removed in LangChain4j `1.19.0`, which Camel Quarkus picked up when aligning with Quarkus LangChain4j `1.13.0`.

Because Quarkus passes a bare `--link-at-build-time`, the unresolvable type fails native image analysis of `LangChain4jMcpServerDefinition.buildTransport`:

```
Error: Discovered unresolved type during parsing: dev.langchain4j.mcp.client.transport.http.HttpMcpTransport$Builder.
This error is reported at image build time because class
org.apache.camel.component.langchain4j.agent.LangChain4jMcpServerDefinition is registered for linking at image build time
by command line and command line.
Error encountered while parsing org.apache.camel.component.langchain4j.agent.LangChain4jMcpServerDefinition.buildClient(LangChain4jMcpServerDefinition.java:208)
```

As a workaround, `LangChain4jMcpServerDefinitionSubstitutions` in `camel-quarkus-support-langchain4j` substitutes `buildTransport` to drop the `sse` branch. The substitution duplicates the upstream method body for the remaining transports, so it will drift if Camel changes that code.

Note that in JVM mode the `sse` transport type fails with `NoClassDefFoundError`, since the substitution applies to native mode only.

Once Camel drops its usage of `HttpMcpTransport`, the following can be removed:

* `extensions-support/langchain4j/runtime/src/main/java/org/apache/camel/quarkus/component/support/langchain4j/graal/LangChain4jMcpServerDefinitionSubstitutions.java`
* The `org.graalvm.sdk:nativeimage` dependency in `extensions-support/langchain4j/runtime/pom.xml`, if nothing else needs it
* `extensions/langchain4j-agent/runtime/src/main/doc/limitations.adoc`

Start by checking whether Camel has dropped its HttpMcpTransport usage, then inspect LangChain4jMcpServerDefinitionSubstitutions.java, extensions-support/langchain4j/runtime/pom.xml, and extensions/langchain4j-agent/runtime/src/main/doc/limitations.adoc. Done means the obsolete substitution and any now-unused nativeimage dependency or limitation text are removed, with no remaining references to the removed transport class.

Written by the indexing model from the issue text.