chore!: allow coder MCP tools to not be injected (#20713)

Currently, when AI Bridge is enabled AND the `oauth2` and
`mcp-server-http` experiments are enabled we inject Coder's MCP tools
into all intercepted AI Bridge requests.

This PR introduces a config to control this behaviour.

**NOTE:** this is a backwards-incompatible change; previously these
tools would be injected automatically, now this setting will need to be
explicitly enabled.

---------

Signed-off-by: Danny Kopping <danny@coder.com>

docs/reference/api/general.md

@@ -175,6 +175,7 @@ curl -X GET http://coder-server:8080/api/v2/deployment/config \
           "small_fast_model": "string"
         },
         "enabled": true,
+        "inject_coder_mcp_tools": true,
         "openai": {
           "base_url": "string",
           "key": "string"