Fix signal-add-sub! losing subscribers after remove, fix build pipeline

signal-add-sub! used (append! subscribers f) which returns a new list
for immutable List but discards the result — after signal-remove-sub!
replaces the subscribers list via dict-set!, re-adding subscribers
silently fails. Counter island only worked once (0→1 then stuck).

Fix: use (dict-set! s "subscribers" (append ...)) to explicitly update
the dict field, matching signal-remove-sub!'s pattern.

Build pipeline fixes:
- sx-build-all.sh now bundles spec→dist and recompiles .sxbc bytecode
- compile-modules.js syncs .sx source files alongside .sxbc to wasm/sx/
- Per-file cache busting: wasm, platform JS, and sxbc each get own hash
- bundle.sh adds cssx.sx to dist

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shared/sx/helpers.py

@@ -883,7 +883,9 @@ def _get_shell_static() -> dict[str, Any]:
         pages_sx=pages_sx,
         sx_css=sx_css,
         sx_css_classes=sx_css_classes,
-        wasm_hash=_wasm_hash("sx_browser.bc.js"),
+        wasm_hash=_wasm_hash("sx_browser.bc.wasm.js"),
+        platform_hash=_wasm_hash("sx-platform-2.js"),
+        sxbc_hash=_sxbc_hash(),
         asset_url=_ca.config.get("ASSET_URL", "/static"),
         inline_css=_shell_cfg.get("inline_css"),
         inline_head_js=_shell_cfg.get("inline_head_js"),
@@ -1032,7 +1034,9 @@ def sx_page_streaming_parts(ctx: dict, page_html: str, *,
     from quart import current_app
     pages_sx = _build_pages_sx(current_app.name)
 
-    wasm_hash = _wasm_hash("sx_browser.bc.js")
+    wasm_hash = _wasm_hash("sx_browser.bc.wasm.js")
+    platform_hash = _wasm_hash("sx-platform-2.js")
+    sxbc_hash = _sxbc_hash()
 
     # Shell: head + body with server-rendered HTML (not SX mount script)
     shell = (
@@ -1074,7 +1078,7 @@ def sx_page_streaming_parts(ctx: dict, page_html: str, *,
     tail = (
         _SX_STREAMING_BOOTSTRAP + '\n'
         + f'<script src="{asset_url}/wasm/sx_browser.bc.wasm.js?v={wasm_hash}"></script>\n'
-          f'<script src="{asset_url}/wasm/sx-platform.js?v={wasm_hash}"></script>\n'
+          f'<script src="{asset_url}/wasm/sx-platform-2.js?v={platform_hash}" data-sxbc-hash="{sxbc_hash}"></script>\n'
     )
 
     return shell, tail
@@ -1124,6 +1128,21 @@ def _wasm_hash(filename: str) -> str:
     return _SCRIPT_HASH_CACHE[key]
 
 
+def _sxbc_hash() -> str:
+    """Compute combined MD5 hash of all .sxbc files, cached for process lifetime."""
+    key = "sxbc/_combined"
+    if key not in _SCRIPT_HASH_CACHE:
+        try:
+            sxbc_dir = Path(__file__).resolve().parent.parent / "static" / "wasm" / "sx"
+            h = hashlib.md5()
+            for p in sorted(sxbc_dir.glob("*.sxbc")):
+                h.update(p.read_bytes())
+            _SCRIPT_HASH_CACHE[key] = h.hexdigest()[:8]
+        except OSError:
+            _SCRIPT_HASH_CACHE[key] = "dev"
+    return _SCRIPT_HASH_CACHE[key]
+
+
 def _get_csrf_token() -> str:
     """Get the CSRF token from the current request context."""
     try:

shared/sx/ocaml_bridge.py

@@ -190,7 +190,8 @@ class OcamlBridge:
         # Only inject small, safe values as kernel variables.
         # Large/complex blobs use placeholder tokens at render time.
         for key in ("component_hash", "sx_css_classes", "asset_url",
-                    "sx_js_hash", "body_js_hash", "wasm_hash"):
+                    "sx_js_hash", "body_js_hash", "wasm_hash",
+                    "platform_hash", "sxbc_hash"):
             val = static.get(key) or ""
             var = f"__shell-{key.replace('_', '-')}"
             defn = f'(define {var} "{_escape(str(val))}")'
@@ -269,6 +270,7 @@ class OcamlBridge:
             placeholders = {}
             static_keys = {"component_hash", "sx_css_classes", "asset_url",
                            "sx_js_hash", "body_js_hash", "wasm_hash",
+                           "platform_hash", "sxbc_hash",
                            "head_scripts", "body_scripts"}
             # page_source is SX wire format that may contain \" escapes.
             # Send via binary blob protocol to avoid double-escaping

shared/sx/templates/shell.sx

@@ -13,6 +13,8 @@
     (body-html :as string?)
     (asset-url :as string)
     (wasm-hash :as string?)
+    (platform-hash :as string?)
+    (sxbc-hash :as string?)
     (inline-css :as string?)
     (inline-head-js :as string?)
     (init-sx :as string?))
@@ -74,8 +76,12 @@
           :type "text/sx"
           :data-mount "#sx-root"
           (raw! (or page-sx "")))
-        (let
-          ((wv (or wasm-hash "0")))
-          (<>
-            (script :src (str asset-url "/wasm/sx_browser.bc.wasm.js?v=" wv))
-            (script :src (str asset-url "/wasm/sx-platform-2.js?v=" wv))))))))
+        (<>
+          (script
+            :src (str
+              asset-url
+              "/wasm/sx_browser.bc.wasm.js?v="
+              (or wasm-hash "0")))
+          (script
+            :src (str asset-url "/wasm/sx-platform-2.js?v=" (or platform-hash "0"))
+            :data-sxbc-hash (or sxbc-hash "0")))))))