docs: remove SSE transport and rename to Streamable HTTP (#6319)

Signed-off-by: Adrian Cole <adrian@tetrate.io>

documentation/docs/guides/goose-cli-commands.md

@@ -110,8 +110,7 @@ Start or resume interactive chat sessions.
 
 **Extension Options:**
 - **`--with-extension <command>`**: Add stdio extensions
-- **`--with-remote-extension <url>`**: Add remote extensions over SSE
-- **`--with-streamable-http-extension <url>`**: Add remote extensions over Streaming HTTP
+- **`--with-streamable-http-extension <url>`**: Add remote extensions over Streamable HTTP
 - **`--with-builtin <id>`**: Enable built-in extensions (e.g., 'developer', 'computercontroller')
 
 **Usage:**
@@ -128,13 +127,12 @@ goose session --resume --path ./session.jsonl   # legacy session storage
 # Start with extensions
 goose session --with-extension "npx -y @modelcontextprotocol/server-memory"
 goose session --with-builtin developer
-goose session --with-remote-extension "http://localhost:8080/sse"
+goose session --with-streamable-http-extension "http://localhost:8080/mcp"
 
 # Advanced: Mix multiple extension types
 goose session \
   --with-extension "echo hello" \
-  --with-remote-extension "http://sse.example.com/sse" \
-  --with-streamable-http-extension "http://http.example.com" \
+  --with-streamable-http-extension "http://localhost:8080/mcp" \
   --with-builtin "developer"
 
 # Control session behavior
@@ -303,8 +301,7 @@ Execute commands from an instruction file or stdin. Check out the [full guide](/
 
 **Extension Options:**
 - **`--with-extension <COMMAND>`**: Add stdio extensions (can be used multiple times)
-- **`--with-remote-extension <URL>`**: Add remote extensions over SSE (can be used multiple times)
-- **`--with-streamable-http-extension <URL>`**: Add remote extensions over Streaming HTTP (can be used multiple times)
+- **`--with-streamable-http-extension <URL>`**: Add remote extensions over Streamable HTTP (can be used multiple times)
 - **`--with-builtin <name>`**: Add builtin extensions by name (e.g., 'developer' or multiple: 'developer,github')
 
 **Control Options:**

documentation/docs/guides/recipes/recipe-reference.md

@@ -170,7 +170,6 @@ The `extensions` field allows you to specify which Model Context Protocol (MCP)
 #### Extension Types
 
 - **`stdio`**: Standard I/O client with command and arguments
-- **`sse`**: Server-sent events client with a URI endpoint  
 - **`builtin`**: Built-in extension that is part of the bundled goose MCP server
 - **`platform`**: Platform extensions that run in the agent process
 - **`streamable_http`**: Streamable HTTP client with URI endpoint

documentation/docs/guides/running-tasks.md

@@ -120,12 +120,6 @@ goose run --with-builtin "developer,computercontroller" -t "your instructions"
 goose run --with-extension "ENV1=value1 custom-extension-args" -t "your instructions"
 ```
 
-- Using remote SSE extensions
-
-```bash
-goose run --with-remote-extension "url" -t "your instructions"
-```
-
 - Using streamable HTTP extensions
 
 ```bash