host: view + edit the SX source of each blog post (blog 47/47, 213 total)

Posts ARE SX source, so expose it: a public raw-source view and a guarded
in-browser source editor.

- GET /<slug>/source  — raw sx_content as text/plain (public; a published
  post's source isn't secret).
- GET /<slug>/edit    — edit form pre-filled with the post's title, raw source
  (in a textarea, render-to-html-escaped so it shows verbatim), and status
  (current value pre-selected). Guarded (editor only). Slug is preserved.
- POST /<slug>/edit   — save the edited source; same write-time validation as
  create (unparseable body -> 400, post left intact); 303 back to the post.
- post page gains "view source · edit · all posts" footer links.

Routing: /:slug/source + /:slug/edit are two-segment patterns; the router
consumes :param as exactly one segment and requires a full match, so /:slug
does not shadow them (asserted). 14 new blog tests cover view (200/text-plain/
raw body/404/no-shadow) and edit (401 unauth GET+POST, 200 form, source shown,
303 save, persisted, slug preserved, 400 malformed, 404 missing).

Verified live on blog.rose-ash.com: view source, guarded edit form, save
round-trip (rendered post + source both reflect the edit).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/host/blog.sx

@@ -107,7 +107,15 @@
         (if r
           (dream-html
             (host/blog--page (get r :title)
-              (quasiquote (article (raw! (unquote (host/blog-render r)))))))
+              (quasiquote
+                (div
+                  (article (raw! (unquote (host/blog-render r))))
+                  (p :style "margin-top:2em;font-size:0.9em;opacity:0.8"
+                    (a :href (unquote (str "/" slug "/source")) "view source")
+                    " · "
+                    (a :href (unquote (str "/" slug "/edit")) "edit")
+                    " · "
+                    (a :href "/" "all posts"))))))
           (dream-html-status 404
             (host/blog--page "Not found"
               (quasiquote
@@ -136,6 +144,20 @@
 
 (define host/blog-index (fn (req) (host/ok (host/blog-list))))
 
+;; GET /<slug>/source — the raw sx_content as text/plain. Posts ARE SX source, so
+;; this just hands back the stored markup (public; a published post's source is
+;; not secret). 404 if the post is absent.
+(define host/blog-source
+  (fn (req)
+    (let ((slug (dream-param req "slug")))
+      (let ((r (host/blog-get slug)))
+        (if r
+          (dream-response 200 {:content-type "text/plain; charset=utf-8"}
+            (or (get r :sx-content) ""))
+          (dream-html-status 404
+            (host/blog--page "Not found"
+              (quasiquote (div (h1 "404") (p (unquote (str "No post: " slug))))))))))))
+
 ;; ── create page (GET /new) — clean minimal form as an SX tree ───────
 ;; No legacy JS editor, no external assets, no shims. The rich WYSIWYG is a
 ;; future native SX-island editor (Phase 5.2+). Posts to /new.
@@ -243,6 +265,66 @@
         (begin (host/blog-delete! slug) (host/ok {:slug slug :deleted true}))
         (host/error 404 "no such post")))))
 
+;; GET /<slug>/edit — edit form pre-filled with the post's current title, raw
+;; sx_content (in a textarea — render-to-html escapes the text child, so the
+;; browser shows the source verbatim), and status (current value pre-selected).
+;; Guarded: only an editor reaches the editor. Keeps the slug (edits don't re-slug).
+(define host/blog-edit-form
+  (fn (req)
+    (let ((slug (dream-param req "slug")))
+      (let ((r (host/blog-get slug)))
+        (if (nil? r)
+          (dream-html-status 404
+            (host/blog--page "Not found"
+              (quasiquote (div (h1 "404") (p (unquote (str "No post: " slug)))))))
+          (let ((status (get r :status)))
+            (let ((mk-opt
+                    (fn (val label)
+                      (if (= val status)
+                        (quasiquote (option :value (unquote val) :selected "selected" (unquote label)))
+                        (quasiquote (option :value (unquote val) (unquote label)))))))
+              (dream-html
+                (host/blog--page (str "Edit: " (get r :title))
+                  (quasiquote
+                    (div
+                      (h1 (unquote (str "Edit: " (get r :title))))
+                      (form :method "post" :action (unquote (str "/" slug "/edit"))
+                        (p (input :name "title" :value (unquote (get r :title))
+                             :style "font-size:1.4em;width:100%"))
+                        (p (textarea :name "sx_content" :rows "16"
+                             :style "width:100%;font-family:monospace"
+                             (unquote (or (get r :sx-content) ""))))
+                        (p (select :name "status"
+                             (unquote (mk-opt "draft" "Draft"))
+                             (unquote (mk-opt "published" "Published")))
+                          " "
+                          (button :type "submit" "Save")))
+                      (p (a :href (unquote (str "/" slug "/")) "view post")
+                        " · "
+                        (a :href (unquote (str "/" slug "/source")) "view source")))))))))))))
+
+;; POST /<slug>/edit — save the edited source. Same write-time validation as the
+;; create paths (unparseable body -> 400, post left intact). Slug is preserved.
+(define host/blog-edit-submit
+  (fn (req)
+    (let ((slug (dream-param req "slug")))
+      (let ((r (host/blog-get slug)))
+        (if (nil? r)
+          (dream-html-status 404
+            (host/blog--page "Not found"
+              (quasiquote (div (h1 "404") (p (unquote (str "No post: " slug)))))))
+          (let ((title (or (dream-form-field req "title") (get r :title)))
+                (sx-content (or (dream-form-field req "sx_content") ""))
+                (status (or (dream-form-field req "status") (get r :status))))
+            (if (host/blog-content-ok? sx-content)
+              (begin
+                (host/blog-put! slug title sx-content status)
+                (dream-redirect (str "/" slug "/")))
+              (dream-html-status 400
+                (host/blog--page "Error"
+                  (quasiquote (div (h1 "Error") (p "Post body is not valid SX markup.")
+                                (p (a :href (unquote (str "/" slug "/edit")) "Back")))))))))))))
+
 ;; ── routes ──────────────────────────────────────────────────────────
 ;; Public reads + the create form. /, /posts, /new BEFORE /:slug (catch-all).
 ;; MUST be mounted LAST in the app so domain routes (/feed, /health) win.
@@ -251,6 +333,7 @@
     (dream-get "/" host/blog-home)
     (dream-get "/posts" host/blog-index)
     (dream-get "/new" host/blog-new-form)
+    (dream-get "/:slug/source" host/blog-source)
     (dream-get "/:slug" host/blog-post)))
 
 ;; Guarded writes: form ingest + JSON create/update/delete behind auth+ACL.
@@ -267,6 +350,8 @@
   (fn (resolve)
     (list
       (dream-post "/new" (host/blog--protect resolve host/blog-form-submit))
+      (dream-get "/:slug/edit" (host/blog--protect resolve host/blog-edit-form))
+      (dream-post "/:slug/edit" (host/blog--protect resolve host/blog-edit-submit))
       (dream-post "/posts" (host/blog--protect resolve host/blog-create))
       (dream-put "/posts/:slug" (host/blog--protect resolve host/blog-update-handler))
       (dream-delete "/posts/:slug" (host/blog--protect resolve host/blog-delete-handler)))))