Island disposal, reactive lists, input binding, and Phase 2 plan

- Effect and computed auto-register disposers with island scope via
  register-in-scope; dispose-islands-in called before every swap point
  (orchestration.sx) to clean up intervals/subscriptions on navigation.
- Map + deref inside islands auto-upgrades to reactive-list for signal-
  bound list rendering. Demo island with add/remove items.
- New :bind attribute for two-way signal-input binding (text, checkbox,
  radio, textarea, select). bind-input in adapter-dom.sx handles both
  signal→element (effect) and element→signal (event listener).
- Phase 2 plan page at /reactive-islands/phase2 covering input binding,
  keyed reconciliation, reactive class/style, refs, portals, error
  boundaries, suspense, and transitions.
- Updated status tables in overview and plan pages.
- Fixed stopwatch reset (fn body needs do wrapper for multiple exprs).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/ref/orchestration.sx

@@ -261,6 +261,7 @@
               ;; Process OOB swaps
               (process-oob-swaps container
                 (fn (t oob s)
+                  (dispose-islands-in t)
                   (swap-dom-nodes t oob s)
                   (sx-hydrate t)
                   (process-elements t)))
@@ -269,6 +270,8 @@
                     (content (if select-sel
                                (select-from-container container select-sel)
                                (children-to-fragment container))))
+                ;; Dispose old islands before swap
+                (dispose-islands-in target)
                 ;; Swap
                 (with-transition use-transition
                   (fn ()
@@ -282,6 +285,8 @@
     (let ((doc (dom-parse-html-document text)))
       (when doc
         (let ((select-sel (dom-get-attr el "sx-select")))
+          ;; Dispose old islands before swap
+          (dispose-islands-in target)
           (if select-sel
             ;; Select from parsed document
             (let ((html (select-html-from-doc doc select-sel)))
@@ -295,6 +300,7 @@
               ;; Process OOB swaps
               (process-oob-swaps container
                 (fn (t oob s)
+                  (dispose-islands-in t)
                   (swap-dom-nodes t oob s)
                   (post-swap t)))
               ;; Hoist head elements
@@ -816,6 +822,7 @@
     ;; Swap rendered DOM content into target and run post-processing.
     ;; Shared by pure and data page client routes.
     (do
+      (dispose-islands-in target)
       (dom-set-text-content target "")
       (dom-append target rendered)
       (hoist-head-elements-full target)
@@ -1003,6 +1010,7 @@
           (use-transition (get swap-spec "transition"))
           (trimmed (trim data)))
       (when (not (empty? trimmed))
+        (dispose-islands-in target)
         (if (starts-with? trimmed "(")
           ;; SX response
           (let ((rendered (sx-render trimmed))