Fix island SSR: rename signal special form, remove cek-try swallowing

Root cause: the new conditions system's 'signal' special form shadowed
the reactive 'signal' function. (signal 0) in island bodies raised
'Unhandled condition: 0' instead of creating a signal dict.

Fix: rename condition special form to 'signal-condition' in the CEK
dispatcher. The reactive 'signal' function now works normally.

adapter-html.sx: remove cek-try that swallowed island render errors.
Islands now render directly — errors propagate for debugging.

sx_render.ml: add sx_render_to_html that calls SX adapter via CEK.

Results: 4/5 island SSR tests pass:
- Header island: logo, tagline, styled elements ✓
- Navigation buttons ✓
- Geography content ✓
- Stepper: partially renders (code view OK, ~cssx/tw in heading)

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

hosts/ocaml/lib/sx_render.ml

@@ -97,6 +97,16 @@ let render_to_html_ref : (value -> env -> string) ref =
 
 let render_to_html expr env = !render_to_html_ref expr env
 
+(** Render via the SX adapter (render-to-html from adapter-html.sx).
+    Falls back to the native ref if the SX adapter isn't loaded. *)
+let sx_render_to_html render_env expr eval_env =
+  if env_has render_env "render-to-html" then
+    let fn = env_get render_env "render-to-html" in
+    let result = Sx_ref.cek_call fn (List [expr; Env eval_env]) in
+    match result with String s -> s | RawHTML s -> s | _ -> Sx_runtime.value_to_str result
+  else
+    render_to_html expr eval_env
+
 let render_children children env =
   String.concat "" (List.map (fun c -> render_to_html c env) children)
 

tests/playwright/island-ssr.spec.js

@@ -0,0 +1,105 @@
+// Island SSR tests — verify islands render content server-side
+// These tests disable JavaScript to verify pure SSR output.
+
+const { test, expect } = require('playwright/test');
+const BASE_URL = process.env.SX_TEST_URL || 'http://localhost:8013';
+
+test.describe('Island SSR', () => {
+
+  test('header island renders logo and tagline without JavaScript', async ({ browser }) => {
+    const context = await browser.newContext({ javaScriptEnabled: false });
+    const page = await context.newPage();
+    await page.goto(BASE_URL + '/sx/(geography)', { waitUntil: 'domcontentloaded' });
+
+    // The header island should contain rendered HTML, not empty
+    const header = page.locator('[data-sx-island="layouts/header"]');
+    await expect(header).not.toBeEmpty();
+
+    // Should contain the logo text
+    const headerText = await header.textContent();
+    expect(headerText).toContain('sx');
+
+    // Should contain the tagline
+    expect(headerText).toContain('reactive');
+
+    // Should contain copyright
+    expect(headerText).toContain('Giles Bradshaw');
+
+    await context.close();
+  });
+
+  test('header island has styled elements without JavaScript', async ({ browser }) => {
+    const context = await browser.newContext({ javaScriptEnabled: false });
+    const page = await context.newPage();
+    await page.goto(BASE_URL + '/sx/(geography)', { waitUntil: 'domcontentloaded' });
+
+    // The header should have actual HTML elements, not raw SX text
+    const header = page.locator('[data-sx-island="layouts/header"]');
+    const links = await header.locator('a').count();
+    expect(links).toBeGreaterThan(0);
+
+    // Should NOT contain raw SX calls
+    const text = await header.textContent();
+    expect(text).not.toContain('(~');
+    expect(text).not.toContain(':tokens');
+
+    await context.close();
+  });
+
+  test('home stepper island renders content without JavaScript', async ({ browser }) => {
+    const context = await browser.newContext({ javaScriptEnabled: false });
+    const page = await context.newPage();
+    await page.goto(BASE_URL + '/sx/', { waitUntil: 'domcontentloaded' });
+
+    // The stepper island should contain rendered HTML
+    const stepper = page.locator('[data-sx-island="home/stepper"]');
+    await expect(stepper).not.toBeEmpty();
+
+    // Should have actual content — not be 0 bytes
+    const text = await stepper.textContent();
+    expect(text.length).toBeGreaterThan(10);
+
+    // Should NOT show raw SX component calls
+    expect(text).not.toContain('~cssx/tw');
+    expect(text).not.toContain('(div');
+    expect(text).not.toContain(':tokens');
+
+    await context.close();
+  });
+
+  test('island SSR includes navigation buttons', async ({ browser }) => {
+    const context = await browser.newContext({ javaScriptEnabled: false });
+    const page = await context.newPage();
+    await page.goto(BASE_URL + '/sx/', { waitUntil: 'domcontentloaded' });
+
+    // Navigation buttons should be rendered server-side
+    const navLinks = page.locator('a[href*="/sx/("]');
+    const count = await navLinks.count();
+    expect(count).toBeGreaterThan(3);
+
+    // At least Geography, Language, Applications should be visible
+    const bodyText = await page.textContent('body');
+    expect(bodyText).toContain('Geography');
+    expect(bodyText).toContain('Language');
+    expect(bodyText).toContain('Applications');
+
+    await context.close();
+  });
+
+  test('geography page renders full content without JavaScript', async ({ browser }) => {
+    const context = await browser.newContext({ javaScriptEnabled: false });
+    const page = await context.newPage();
+    await page.goto(BASE_URL + '/sx/(geography)', { waitUntil: 'domcontentloaded' });
+
+    // Main content should have the Geography heading
+    const heading = page.locator('h1, h2');
+    await expect(heading.first()).toContainText('Geography');
+
+    // Should have the Rendering Pipeline section
+    const body = await page.textContent('body');
+    expect(body).toContain('Rendering Pipeline');
+    expect(body).toContain('OCaml');
+
+    await context.close();
+  });
+});

web/adapter-html.sx

@@ -532,7 +532,7 @@
             (make-raw-html
               (join "" (map (fn (c) (render-to-html c env)) children)))))
         (let
-          ((body-html (cek-try (fn () (render-to-html (component-body island) local)) (fn (err) "")))
+          ((body-html (render-to-html (component-body island) local))
             (state-sx (serialize-island-state kwargs)))
           (str
             "<span data-sx-island=\""