config(fish): add full fish config from live home; portable clipboard + env guards

Keep starship prompt (omp migration rejected). cpy/pst aliases branch on
wl-copy vs pbcopy; functions use the aliases. BROWSER/CHROME_EXECUTABLE
guarded on binary existence. auto-Niri.fish and cp-appid.fish are
linux-only (gated in .chezmoiignore).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

dot_config/fish/functions/clip-last.fish

@@ -1,4 +1,4 @@
 function clip-last --description 'Re-run last command, copy output to clipboard'
-    eval $history[1] | wl-copy
+    eval $history[1] | cpy
     notify-send -a fish "Clipboard" "Command output copied to clipboard"
 end