remove q quit alias

`q` was introduced in round-5 as a peer Keyword variant alongside
`quit`. Per ADR-0023's "alias miss" critique, that was the wrong
shape — it surfaced `q` as a standalone command in completion
(only one of its kind), and required parallel parser + usage +
catalog + test entries. Drops the Keyword variant entirely; if
this ever needs to come back, it should arrive as an alias
annotation per ADR-0023, not as a peer keyword.

Tests still 769 passing.

src/friendly/keys.rs

@@ -220,7 +220,6 @@ pub const KEYS_AND_PLACEHOLDERS: &[(&str, &[&str])] = &[
     ("parse.token.keyword.null", &[]),
     ("parse.token.keyword.on", &[]),
     ("parse.token.keyword.pk", &[]),
-    ("parse.token.keyword.q", &[]),
     ("parse.token.keyword.quit", &[]),
     ("parse.token.keyword.rebuild", &[]),
     ("parse.token.keyword.relationship", &[]),