Leave the migration guide alone; these are 2.x fixes, not v1->v2 breaks

The migration guide documents breaking changes between majors. Nothing here
changes a signature or documented behaviour, so the notes belong in the release
notes, not the guide.

No-Verification-Needed: docs-only revert

Author: maxisbey

docs/migration.md

@@ -668,7 +668,7 @@ All submodules under `mcp.server.fastmcp.*` are now under `mcp.server.mcpserver.
 
 - `Image`, `Audio` — from `mcp.server.mcpserver` (or `.utilities.types`)
 - `Icon` — from `mcp.server.mcpserver` or `mcp.types` (not a top-level `mcp` export); its `mimeType` field is now `mime_type` per the [snake_case renames](#field-names-changed-from-camelcase-to-snake_case), though the `mimeType=` kwarg still constructs
-- `Message`, `UserMessage`, `AssistantMessage` — from `mcp.server.mcpserver` (or `.prompts.base`)
+- `Message`, `UserMessage`, `AssistantMessage` — from `mcp.server.mcpserver.prompts.base`
 - `ToolError`, `ResourceError` — from `mcp.server.mcpserver.exceptions`
 - `MCPServerError` (renamed from `FastMCPError`) — from `mcp.server.mcpserver.exceptions`
 
@@ -677,8 +677,8 @@ All submodules under `mcp.server.fastmcp.*` are now under `mcp.server.mcpserver.
 Beyond the changes covered in this section, the everyday `FastMCP` surface carries over to `MCPServer` as-is:
 
 - **Decorators.** `@mcp.tool()`, `@mcp.resource()`, `@mcp.prompt()`, and `@mcp.completion()` take the same arguments and handler signatures as v1. The lowlevel [`on_completion` reshape](#lowlevel-server-decorator-based-handlers-replaced-with-constructor-on_-params) applies only to the lowlevel `Server`; a high-level `@mcp.completion()` handler is still called as `(ref, argument, context)`.
-- **Tool return handling.** A returned `CallToolResult` (including an `Annotated[CallToolResult, YourModel]` output schema, and `_meta`) is passed through, `Image` and `Audio` convert to content blocks as before, ready-made content blocks are kept as-is (neither is [structured by default](#content-block-image-and-audio-return-annotations-are-unstructured) now, even inside a `list`), and dict, list, scalar, and model returns are wrapped into `content` and `structured_content` by the same rules.
-- **Listing and registration methods.** `list_tools()`, `list_resources()`, `list_resource_templates()`, and `list_prompts()` return the same lists and are still what the protocol handlers call, so subclass overrides still take effect. `add_tool()`, `add_resource()`, and `add_prompt()` are unchanged (`add_prompt()` additionally accepts the plain function, like `add_tool()`).
+- **Tool return handling.** A returned `CallToolResult` (including an `Annotated[CallToolResult, YourModel]` output schema, and `_meta`) is passed through, `Image` and `Audio` convert to content blocks as before, ready-made content blocks are kept as-is, and dict, list, scalar, and model returns are wrapped into `content` and `structured_content` by the same rules.
+- **Listing and registration methods.** `list_tools()`, `list_resources()`, `list_resource_templates()`, and `list_prompts()` return the same lists and are still what the protocol handlers call, so subclass overrides still take effect. `add_tool()`, `add_resource()`, and `add_prompt()` are unchanged.
 - **Helpers.** `Image.to_image_content()`, `Audio.to_audio_content()`, and the prompt `Message`, `UserMessage`, and `AssistantMessage` classes.
 - **Lifespan.** The `lifespan=` constructor argument and `ctx.request_context.lifespan_context` work as before, and the class is still generic over the lifespan result: `FastMCP[MyState]` becomes `MCPServer[MyState]`. (`Context`'s own type parameters did change; see [`RequestContext` type parameters simplified](#requestcontext-type-parameters-simplified).)
 - **Tool internals.** `Tool`, `Tool.from_function()`, `FuncMetadata`, `ArgModelBase`, and `func_metadata()` keep their v1 shapes; the one change is the now-required `context` argument to `Tool.run()`, described [below](#mcpservercall_tool-read_resource-get_prompt-now-accept-a-context-parameter).
@@ -924,22 +924,6 @@ running on the event-loop thread:
 
 Declare the handler `async def` to keep it on the event loop.
 
-### Content-block, `Image`, and `Audio` return annotations are unstructured
-
-A tool whose return annotation mentions a content block (`TextContent`,
-`ImageContent`, `AudioContent`, `ResourceLink`, `EmbeddedResource`), `Image`, or
-`Audio` anywhere (alone, or inside a `list`, `tuple`, or union) now registers
-with no `output_schema` and returns no `structured_content`; `content` is built
-exactly as before. v1 (and 2.0) published the block type's own Pydantic schema as
-the tool's `output_schema` and echoed the serialized blocks into
-`structured_content` a second time, while an annotation with `Image` or `Audio`
-inside a generic (`-> list[Image]`) raised at registration (a bare `-> Image` was
-already unstructured).
-
-If a client reads `structured_content` from such a tool, return a model,
-`TypedDict`, or `dict` instead, or pass `structured_output=True` to keep
-publishing a content block's schema.
-
 ### `MCPServer.call_tool()` returns `CallToolResult`
 
 `MCPServer.call_tool()` now returns a `CallToolResult` (or an