add ssr-counter example demonstrating SSR + hydration end-to-end

Counter.el defines Counter, CounterPair, and App components with {#if}
conditionals, event handlers, and child component composition.

render.js (generated by elc-ui --target=server) is the Node.js render
script the server calls. app.js (generated by elc-ui --target=web) is the
compiled browser module. hydrate.js attaches the runtime to the
server-rendered DOM without replacing it.

index.html shows the integration point with instructions for injecting
server output and the two CLI commands needed to regenerate both targets.

vessels/el-ui-compiler/elc-ui

@@ -218,16 +218,27 @@ function emitComponentClass(comp, components) {
  * @returns {string}
  */
 function transformMethodBody(body, stateNames) {
-    let result = body;
-    for (const name of stateNames) {
-        // Replace bare assignments: name = expr  (not inside ==, !=, <=, >=)
-        const re = new RegExp(`(?<![=!<>])\\b${name}\\s*=(?!=)\\s*`, 'g');
-        result = result.replace(re, `__self.setState('${name}', `);
-        // We need to close the paren — this is tricky without full parsing.
-        // For now, append ) at end of expression line (works for simple cases).
-        // Full statement-level transformation requires the parser.
-    }
-    return result;
+    // Process line-by-line: for each line that contains a bare state assignment,
+    // rewrite: `name = expr` -> `__self.setState('name', expr)`
+    // This is a line-level transformation that works for the common case where
+    // each state assignment is on its own line (the el-ui style).
+    const lines = body.split('\n');
+    const transformed = lines.map(line => {
+        let changed = line;
+        for (const name of stateNames) {
+            // Match: optional whitespace + name + = (not ==, !=, <=, >=) + rest of line
+            const re = new RegExp(`^(\\s*)${name}\\s*=(?![=>])\\s*(.+)$`);
+            const m = changed.match(re);
+            if (m) {
+                // m[1] = leading whitespace, m[2] = RHS expression
+                // Strip trailing newline/whitespace from the RHS
+                const rhs = m[2].trimEnd();
+                changed = `${m[1]}__self.setState('${name}', ${rhs})`;
+            }
+        }
+        return changed;
+    });
+    return transformed.join('\n');
 }
 
 /**