Have read_file support images (#30435)

This is very basic support for them. There are a number of other TODOs
before this is really a first-class supported feature, so not adding any
release notes for it; for now, this PR just makes it so that if
read_file tries to read a PNG (which has come up in practice), it at
least correctly sends it to Anthropic instead of messing up.

This also lays the groundwork for future PRs for more first-class
support for images in tool calls across more image file formats and LLM
providers.

Release Notes:

- N/A

---------

Co-authored-by: Agus Zubiaga <hi@aguz.me>
Co-authored-by: Agus Zubiaga <agus@zed.dev>

crates/assistant_tools/src/edit_agent/evals.rs

@@ -10,8 +10,8 @@ use futures::{FutureExt, future::LocalBoxFuture};
 use gpui::{AppContext, TestAppContext};
 use indoc::{formatdoc, indoc};
 use language_model::{
-    LanguageModelRegistry, LanguageModelRequestTool, LanguageModelToolResult, LanguageModelToolUse,
-    LanguageModelToolUseId,
+    LanguageModelRegistry, LanguageModelRequestTool, LanguageModelToolResult,
+    LanguageModelToolResultContent, LanguageModelToolUse, LanguageModelToolUseId,
 };
 use project::Project;
 use rand::prelude::*;
@@ -951,7 +951,7 @@ fn tool_result(
         tool_use_id: LanguageModelToolUseId::from(id.into()),
         tool_name: name.into(),
         is_error: false,
-        content: result.into(),
+        content: LanguageModelToolResultContent::Text(result.into()),
         output: None,
     })
 }