Fix a bunch of other low-hanging style lints (#36498)

- **Fix a bunch of low hanging style lints like unnecessary-return**
- **Fix single worktree violation**
- **And the rest**

Release Notes:

- N/A

crates/agent2/src/tools/read_file_tool.rs

@@ -175,7 +175,7 @@ impl AgentTool for ReadFileTool {
                 buffer
                     .file()
                     .as_ref()
-                    .map_or(true, |file| !file.disk_state().exists())
+                    .is_none_or(|file| !file.disk_state().exists())
             })? {
                 anyhow::bail!("{file_path} not found");
             }

crates/agent2/src/tools/terminal_tool.rs

@@ -271,7 +271,7 @@ fn working_dir(
     let project = project.read(cx);
     let cd = &input.cd;
 
-    if cd == "." || cd == "" {
+    if cd == "." || cd.is_empty() {
         // Accept "." or "" as meaning "the one worktree" if we only have one worktree.
         let mut worktrees = project.worktrees(cx);
 
@@ -296,10 +296,8 @@ fn working_dir(
             {
                 return Ok(Some(input_path.into()));
             }
-        } else {
-            if let Some(worktree) = project.worktree_for_root_name(cd, cx) {
-                return Ok(Some(worktree.read(cx).abs_path().to_path_buf()));
-            }
+        } else if let Some(worktree) = project.worktree_for_root_name(cd, cx) {
+            return Ok(Some(worktree.read(cx).abs_path().to_path_buf()));
         }
 
         anyhow::bail!("`cd` directory {cd:?} was not in any of the project's worktrees.");