fix(env): address all PR review feedback

- Add settings profiles to zsh env completion (was proxy-only)
- Document intentional ANTHROPIC_MODEL omission in transformToOpenAI
- Use getCcsDir() in error hint instead of hardcoded ~/.ccs/
- Export parseFlag and add 5 unit tests for flag parsing
- Add fish and PowerShell single-quote escaping tests

scripts/completion/ccs.zsh

@@ -130,7 +130,7 @@ _ccs() {
             '--format[Output format]:format:(openai anthropic raw)' \
             '--shell[Shell syntax]:shell:(bash fish powershell)' \
             '(- *)'{-h,--help}'[Show help]' \
-            '1:profile:($proxy_profiles)'
+            '1:profile:($proxy_profiles ${(k)settings_profiles_described})'
           ;;
         gemini|codex|agy|qwen)
           _arguments \