cross-domain UI: allocate operable from the web + real relations + /calendars view

Makes slice 1 clickable and real. The effect DRIVER now PERFORMS action-effects (closing the loop):
a 'relate' effect {:args (src kind dst)} mutates the relation graph. The events calendar behavior's
allocate-link DAG emits (effect relate (field target) 'allocated' (field slug)), so an allocated post
becomes a real main--allocated-->post edge on events (not just a log line).

UI: every blog post page shows an 'Allocate to a calendar' form (host/blog--allocate-form, shown when
a peer is configured) → POST /:slug/allocate reads the form field. events gets a /calendars page
listing posts allocated to 'main'. serve.sh seeds a 'main' calendar (is-a calendar) on events.

LIVE: submit the allocate form on blog.rose-ash.com/welcome → events /calendars shows 'welcome'
allocated to main, a real federated relation. blog 218/218.

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

lib/host/blog.sx

@@ -158,6 +158,16 @@
      :object post :object-type (host/blog--post-type post) :slug post
      :target calendar :to host/blog--events-base
      :delta (str "allocate to " calendar) :id (str "allocate:" post ":" calendar)}))
+;; the UI form to allocate THIS post to a calendar on the events peer (shown only when a peer is set).
+(define host/blog--allocate-form
+  (fn (slug)
+    (if (= host/blog--events-base "") ""
+      (quasiquote
+        (form :method "post" :action (unquote (str "/" slug "/allocate"))
+              :style "margin:1.5em 0;padding:0.7em 1em;border:1px dashed #b9a;background:#fbf7fb;border-radius:4px;font-size:0.9em"
+          (b "📅 Allocate to a calendar: ")
+          (input :name "calendar" :value "main" :style "width:8em")
+          " " (button :type "submit" "Allocate on events"))))))
 ;; MARSHAL the canonical activity → next/'s Erlang proplist shape, for the Erlang runner adapter
 ;; (RA). The seam activity is canonical; each runner adapter maps it to its substrate. Unused until
 ;; RA, defined + tested here so the reconcile is complete and RA has its bridge ready.
@@ -299,13 +309,19 @@
 ;; persisted to the blog store under one key, so /flows survives a restart. Boot-loaded via
 ;; host/blog-load-flowlog!. (Whole-list rewrite per effect — fine at P0 volume; cap/rotate later.)
 (define host/blog--flowlog-key "flowlog")
+;; the DRIVER dispatches effect-as-data. Beyond logging, it PERFORMS known action-effects (closing
+;; the loop — P4): a `relate` effect {:args (src kind dst)} mutates the relation graph, so a behavior
+;; can create real cross-domain links (the events calendar behavior relates calendar→post).
 (define host/blog--driver
   {:dispatch (fn (eff)
-               (begin (set! host/blog--flow-log
-                        (concat host/blog--flow-log
-                          (list {"verb" (get eff :verb) "args" (get eff :args)})))
-                      (persist/backend-kv-put host/blog-store host/blog--flowlog-key host/blog--flow-log)
-                      (list)))})            ;; record the effect (durably); no follow-up activities (P0)
+               (begin
+                 (when (= (get eff :verb) "relate")
+                   (let ((a (get eff :args)))
+                     (host/blog-relate! (first a) (first (rest (rest a))) (first (rest a)))))
+                 (set! host/blog--flow-log
+                   (concat host/blog--flow-log (list {"verb" (get eff :verb) "args" (get eff :args)})))
+                 (persist/backend-kv-put host/blog-store host/blog--flowlog-key host/blog--flow-log)
+                 (list)))})            ;; record the effect (durably); no follow-up activities (P0)
 ;; rebuild the in-memory flow log from the durable store (call on boot, like host/blog-load-edges!).
 (define host/blog-load-flowlog!
   (fn ()
@@ -2364,6 +2380,7 @@
                       (unquote type-def-view)
                       (unquote type-population)
                       (unquote relations)
+                      (unquote (host/blog--allocate-form slug))
                       (p :style "margin-top:2em;font-size:0.9em;opacity:0.8"
                         (a :href (unquote (str "/" slug "/source")) "view source")
                         " · "
@@ -2964,6 +2981,22 @@
                                        (unquote (if (> (len (get e "args")) 0) (str (first (get e "args"))) "")))))
                        host/blog--flow-log))))))))))))
 
+;; ── /calendars — the events domain view: posts allocated to each calendar (federated from blog) ──
+(define host/blog-calendars
+  (fn (req)
+    (host/blog--resp req 200
+      (host/blog--page req "Calendars"
+        (quasiquote
+          (div (h1 "Calendars")
+            (p "Posts allocated to a calendar (federated in from blog, linked by the calendar type's on-allocate behavior).")
+            (h3 :style "margin:1em 0 0.3em" "main")
+            (unquote
+              (let ((posts (host/blog-out "main" "allocated")))
+                (if (= (len posts) 0)
+                  (quote (p :style "color:#999" (em "Nothing allocated yet.")))
+                  (cons (quote ul)
+                    (map (fn (p) (quasiquote (li (unquote (str p))))) posts)))))))))))
+
 ;; ── /activities — P2: the EVENT SOURCE ───────────────────────────────
 ;; Every observable state change emitted as a canonical activity (Create/Update on content,
 ;; Add/Remove on relations). This is what federates (TA pushes it to peers) and what triggers
@@ -3018,6 +3051,7 @@
     (dream-get "/workflow-demo" host/blog-workflow-demo)
     (dream-get "/flows" host/blog-flows)
     (dream-get "/fed-tick" host/blog-fed-tick)
+    (dream-get "/calendars" host/blog-calendars)
     (dream-get "/activities" host/blog-activities)
     (dream-get "/:slug/source" host/blog-source)
     (dream-get "/:slug/relate-options" host/blog-relate-options)
@@ -3041,7 +3075,8 @@
 ;; directed "allocate" activity that federates to events, whose calendar type reacts (P1 behavior).
 (define host/blog-allocate
   (fn (req)
-    (let ((post (dream-param req "slug")) (calendar (or (dream-query-param req "calendar") "main")))
+    (let ((post (dream-param req "slug"))
+          (calendar (or (host/field req "calendar") (dream-query-param req "calendar") "main")))
       (begin
         (when (not (= host/blog--events-base "")) (host/blog--allocate! post calendar))
         (dream-redirect (str "/" post "/"))))))

lib/host/serve.sh

@@ -230,8 +230,15 @@ EPOCH=1
     echo "(epoch $EPOCH)"
     echo "(eval \"(host/blog-seed! \\\"calendar\\\" \\\"Calendar\\\" \\\"(article (h1 \\\\\\\"Calendar\\\\\\\") (p \\\\\\\"Posts allocated to this calendar.\\\\\\\"))\\\" \\\"published\\\")\")"
     EPOCH=$((EPOCH+1))
+    # a concrete calendar instance ("main") posts get allocated to.
     echo "(epoch $EPOCH)"
-    echo "(eval \"(host/blog--register-dag! \\\"allocate-link\\\" (quote (effect linked (field \\\"slug\\\"))))\")"
+    echo "(eval \"(host/blog-seed! \\\"main\\\" \\\"Main Calendar\\\" \\\"(article (h1 \\\\\\\"Main Calendar\\\\\\\"))\\\" \\\"published\\\")\")"
+    EPOCH=$((EPOCH+1))
+    echo "(epoch $EPOCH)"
+    echo "(eval \"(host/blog-relate! \\\"main\\\" \\\"calendar\\\" \\\"is-a\\\")\")"
+    EPOCH=$((EPOCH+1))
+    echo "(epoch $EPOCH)"
+    echo "(eval \"(host/blog--register-dag! \\\"allocate-link\\\" (quote (effect relate (field \\\"target\\\") \\\"allocated\\\" (field \\\"slug\\\"))))\")"
     EPOCH=$((EPOCH+1))
     echo "(epoch $EPOCH)"
     echo "(eval \"(host/blog--set-type-behavior! \\\"calendar\\\" (list {\\\"verb\\\" \\\"allocate\\\" \\\"type\\\" \\\"article\\\" \\\"dag\\\" \\\"allocate-link\\\"}))\")"