fix(docs): escape <no body> in mcp doc-comment so rustdoc accepts it

CI Documentation job was failing with `error: unclosed HTML tag 'no'` at
crates/tui/src/mcp.rs:71. Rustdoc parses unescaped `<no body>` as an HTML
tag and `RUSTDOCFLAGS=-Dwarnings` (used in CI) promotes that to a hard
error. Reword the comment to refer to the literal string instead.

crates/tui/src/mcp.rs

@@ -68,7 +68,7 @@ fn redact_body_preview(body: &str) -> String {
 
 /// Read up to `max_bytes` of a reqwest Response body and produce a single-line
 /// excerpt suitable for an error message. Best-effort — if the body can't be
-/// read, returns "<no body>".
+/// read, returns the literal string `<no body>`.
 async fn bounded_body_excerpt(response: reqwest::Response, max_bytes: usize) -> String {
     let body_text = response.text().await.unwrap_or_default();
     if body_text.is_empty() {