fix justfiles: quote echo args with parens, remove stale cd kde

- KDE justfile: quote @echo arguments containing parentheses (sh syntax)
- KDE justfile: remove 'cd kde &&' prefix from cmake commands (already
  running from kde/ directory when invoked via just -f)
- Root justfile: quote all @echo arguments with parentheses
- KDE justfile: fix cmake install prefix and j*(nproc) typo

justfile

@@ -50,7 +50,7 @@ kde:
     just -f kde/justfile kde
 
 kde-kf5:
-    @echo === Building ollie-kde (KF5) ===
+    @echo '=== Building ollie-kde (KF5) ==='
     just -f kde/justfile kde-kf5
 
 # === Install targets ===
@@ -62,15 +62,15 @@ install: test install-data install-scripts install-contrib install-kde install-e
 
 install-kf5: test install-data install-scripts install-contrib install-kde-kf5 install-el
     install -m644 contrib/prompts/session-9p.md {{cfg}}/prompts/session.md
-    @echo === Install complete (KF5) ===
+    @echo '=== Install complete (KF5) ==='
     @echo 'Restart Plasma to pick up KDE plugins.'
 
 install-kde:
-    @echo === Installing ollie-kde (KF6) ===
+    @echo '=== Installing ollie-kde (KF6) ==='
     just -f kde/justfile install-kde
 
 install-kde-kf5:
-    @echo === Installing ollie-kde (KF5) ===
+    @echo '=== Installing ollie-kde (KF5) ==='
     just -f kde/justfile install-kde-kf5
 
 install-el:
@@ -224,7 +224,7 @@ uninstall:
     @echo === Uninstall complete ===
 
 uninstall-kf5:
-    @echo === Uninstalling ollie (KF5) ===
+    @echo '=== Uninstalling ollie (KF5) ==='
     rm -f {{bin}}/Ollie {{bin}}/Kmpl {{bin}}/Oi {{bin}}/Theo
     rm -f {{bin}}/ollie-remount {{bin}}/ollie-watchdog
     rm -rf {{cfg}}
@@ -237,7 +237,7 @@ uninstall-kf5:
     rm -rf ~/.config/emacs/ellie
     # Plasma env
     rm -f ~/.config/plasma-workspace/env/99-ollie.sh
-    @echo === Uninstall complete (KF5) ===
+    @echo '=== Uninstall complete (KF5) ==='
 
 # === Test targets ===