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

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

plans/dream-on-sx.md

@@ -119,6 +119,11 @@ with extensions + hardening below.
   wrong-secret cookie yields a fresh session instead of a hijack. `dream-cookie-sign` /
   `dream-cookie-unsign` (keyed hash; same not-cryptographic caveat — inject a host HMAC
   in production). Plain `dream-sessions` unchanged for the no-secret case.
+- **2026-06-07 — Ext: query/header convenience** (`lib/dream/types.sx`, types suite
+  41→59, 358 total). `dream-queries`, `dream-query-param-or` / `dream-header-or` /
+  `dream-param-or` (defaults), `dream-has-query?` / `-header?` / `-param?`,
+  `dream-content-type-of`, `dream-method-is?`, `dream-accepts?` / `dream-wants-json?`
+  (Accept-header content negotiation).
 
 ## Extensions (post-roadmap)
 
@@ -131,7 +136,7 @@ The five-types core is complete; these harden it toward a production HTTP front
 - [x] **Error-handling middleware** (`dream-catch` / custom 500 templates; `guard`-based).
 - [x] **Signed session cookies** (`dream-sessions-signed` — tamper-evident sid).
 - [x] **JSON helpers** (encode + recursive-descent parse, pure SX).
-- [ ] **Query/header convenience** (`dream-queries`, defaults).
+- [x] **Query/header convenience** (`dream-queries`, `*-or` defaults, `dream-accepts?`).
 - [ ] **`api.sx` facade + README** — single load point listing the public surface.
 
 ## Stdlib additions Dream will need