dream: query/header convenience helpers + content negotiation + 18 tests

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/dream/types.sx

@@ -93,6 +93,35 @@
         (keys more)))))
 (define dream-set-body (fn (req body) (assoc req :body body)))
 
+;; ── request convenience ────────────────────────────────────────────
+(define dream-queries (fn (req) (get req :query)))
+(define
+  dream-query-param-or
+  (fn (req name default) (or (dream-query-param req name) default)))
+(define dream-has-query? (fn (req name) (has-key? (get req :query) name)))
+(define
+  dream-header-or
+  (fn (req name default) (or (dream-header req name) default)))
+(define
+  dream-has-header?
+  (fn (req name) (has-key? (get req :headers) (lower name))))
+(define
+  dream-param-or
+  (fn (req name default) (or (dream-param req name) default)))
+(define dream-has-param? (fn (req name) (has-key? (get req :params) name)))
+(define dream-content-type-of (fn (req) (dream-header req "content-type")))
+(define dream-method-is? (fn (req m) (= (dream-method req) (upper m))))
+(define
+  dream-accepts?
+  (fn
+    (req mime)
+    (let
+      ((a (dream-header req "accept")))
+      (if a (contains? a mime) false))))
+(define
+  dream-wants-json?
+  (fn (req) (dream-accepts? req "application/json")))
+
 ;; ── response ───────────────────────────────────────────────────────
 (define dream-response (fn (status headers body) {:body body :headers (dr/normalize-headers headers) :status status}))