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/strings/en-US.yaml

@@ -190,7 +190,7 @@ help:
                                  <project-path>.
 
     App-level commands (typed inside the app, available in both modes):
-        quit / q                 Exit cleanly.
+        quit                     Exit cleanly.
         mode simple|advanced     Switch input mode.
         help                     Show this list of commands in-app.
         save                     Save the current temp project under a
@@ -214,7 +214,7 @@ help:
   # math stays accurate.
   in_app_body: |
     Supported commands:
-      quit / q              — exit
+      quit                  — exit
       help                  — this list
       mode simple|advanced  — switch input mode
       messages              — show current verbosity
@@ -355,7 +355,7 @@ parse:
     # grammar that the parser accepts; the in-app `help`
     # listing in `help.in_app_body` carries the user-facing
     # description.
-    quit: "quit  |  q"
+    quit: "quit"
     help: "help"
     rebuild: "rebuild"
     save: "save  |  save as"
@@ -406,7 +406,6 @@ parse:
       # App-lifecycle commands (per ADR-0003, surfaced through
       # the parser to drive completion + usage templates).
       quit: "`quit`"
-      q: "`q`"
       help: "`help`"
       rebuild: "`rebuild`"
       save: "`save`"