Fix unsafe error handling in edge functions, add lint to CI

- Edge functions used err.message without checking err type, which
  throws if the caught value is not an Error object
- Add lint step to CI pipeline before build

Author: Ekin-Kahraman

.github/workflows/ci.yml

@@ -16,5 +16,6 @@ jobs:
           node-version: 20
           cache: npm
       - run: npm ci
+      - run: npm run lint
       - run: npm run build
       - run: npm test

supabase/functions/process-response/index.ts

@@ -141,7 +141,7 @@ Please review urgently.
   } catch (err) {
     console.error("process-response error:", err);
     return new Response(
-      JSON.stringify({ error: err.message }),
+      JSON.stringify({ error: err instanceof Error ? err.message : String(err) }),
       { status: 500, headers: { ...corsHeaders, "Content-Type": "application/json" } }
     );
   }

supabase/functions/trigger-followup/index.ts

@@ -115,7 +115,7 @@ If this is a medical emergency call 999.
   } catch (err) {
     console.error("trigger-followup error:", err);
     return new Response(
-      JSON.stringify({ error: err.message }),
+      JSON.stringify({ error: err instanceof Error ? err.message : String(err) }),
       { status: 500, headers: { ...corsHeaders, "Content-Type": "application/json" } }
     );
   }