fix: cl-dotenv quote contamination breaks provider cascade parsing

cl-dotenv preserves surrounding quotes in .env values (unlike bash).
PROVIDER_CASCADE="deepseek,..." resulted in keywords like :"DEEPSEEK
instead of :DEEPSEEK, causing all cascade lookups to fail silently.

Fixes:
- .env.example: remove quotes from PROVIDER_CASCADE
- provider-cascade-initialize: add #" and #' to string-trim chars
- system-model-router: same fix for LOCAL_BACKENDS parsing

.env.example

@@ -20,7 +20,7 @@ NVIDIA_API_KEY="your_nvidia_nim_key_here"
 
 # Cascade order (first available provider wins)
 # Default (if unset): openrouter,openai,anthropic,groq,gemini-api,deepseek,nvidia
-PROVIDER_CASCADE="deepseek,openrouter,openai,anthropic,groq,gemini,nvidia"
+PROVIDER_CASCADE=deepseek,openrouter,openai,anthropic,groq,gemini,nvidia
 
 # =============================================================================
 # LOCAL LLM (generic OpenAI-compatible endpoint)

lisp/system-model-provider.lisp

@@ -81,7 +81,7 @@
   (let ((cascade-str (uiop:getenv "PROVIDER_CASCADE")))
     (if cascade-str
         (setf *provider-cascade*
-              (mapcar (lambda (s) (intern (string-upcase (string-trim '(#\Space) s)) :keyword))
+              (mapcar (lambda (s) (intern (string-upcase (string-trim '(#\Space #\" #\') s)) :keyword))
                       (uiop:split-string cascade-str :separator '(#\,))))
         (setf *provider-cascade* (mapcar #'car (remove-if (lambda (e)
                                                              (member (car e) '(:local)))

lisp/system-model-router.lisp

@@ -77,7 +77,7 @@ Returns model name or :skip."
           *model-cascade-background* (parse-cascade (uiop:getenv "MODEL_CASCADE_BACKGROUND"))
           *local-backends* (let ((env (uiop:getenv "LOCAL_BACKENDS")))
                              (if env
-                                 (mapcar (lambda (s) (intern (string-upcase (string-trim " " s)) :keyword))
+                                 (mapcar (lambda (s) (intern (string-upcase (string-trim '(#\Space #\" #\') s)) :keyword))
                                          (uiop:split-string env :separator '(#\,)))
                                  '(:ollama :llama-cpp)))))
     (setf *model-selector* #'model-select)

org/system-model-provider.org

@@ -127,7 +127,7 @@ Providers register themselves at boot. No API key? That provider doesn't registe
   (let ((cascade-str (uiop:getenv "PROVIDER_CASCADE")))
     (if cascade-str
         (setf *provider-cascade*
-              (mapcar (lambda (s) (intern (string-upcase (string-trim '(#\Space) s)) :keyword))
+              (mapcar (lambda (s) (intern (string-upcase (string-trim '(#\Space #\" #\') s)) :keyword))
                       (uiop:split-string cascade-str :separator '(#\,))))
         (setf *provider-cascade* (mapcar #'car (remove-if (lambda (e)
                                                              (member (car e) '(:local)))

org/system-model-router.org

@@ -193,7 +193,7 @@ Reads cascade configuration from environment variables and registers
           *model-cascade-background* (parse-cascade (uiop:getenv "MODEL_CASCADE_BACKGROUND"))
           *local-backends* (let ((env (uiop:getenv "LOCAL_BACKENDS")))
                              (if env
-                                 (mapcar (lambda (s) (intern (string-upcase (string-trim " " s)) :keyword))
+                                 (mapcar (lambda (s) (intern (string-upcase (string-trim '(#\Space #\" #\') s)) :keyword))
                                          (uiop:split-string env :separator '(#\,)))
                                  '(:ollama :llama-cpp)))))
     (setf *model-selector* #'model-select)