Add Live Interpreter page at /repl/ with card on the home page

A public-facing Io REPL in the style of dekorte.com/projects/aiapps:
chat-like transcript (input echoes right, VM output left, exceptions
in error bubbles), one-click examples including live DOM manipulation
via the JS bridge, and a collapsible How It Works section.

The page reuses browser/io.js and io_browser.wasm — io.js gains a
window.IO_WASM_URL override so pages outside browser/ can locate the
wasm. io_browser.c now tracks top-level exceptions with a flag (set
by the exception callback) so do_eval can return status 1; previously
IoState_tryToPerform cleared errorRaised after printing, so uncaught
exceptions reported success and rendered as normal results.

The Pages workflow installs wasi-sdk and runs `make browser` so the
gitignored wasm is built for deploys, and repl/browser/Links paths now
trigger it. Home page card added to _index.json; static HTML
regenerated (the prefetch blob embeds the root index, hence the
sweep across generated pages).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: stevedekorte

.github/workflows/pages.yml

@@ -14,6 +14,9 @@ on:
       - 'FAQ/**'
       - 'Timeline/**'
       - 'images/**'
+      - 'Links/**'
+      - 'repl/**'
+      - 'browser/**'
       - '.github/workflows/pages.yml'
   workflow_dispatch:
 
@@ -29,6 +32,9 @@ concurrency:
 jobs:
   build:
     runs-on: ubuntu-latest
+    env:
+      WASI_SDK_VERSION: "24"
+      WASI_SDK_FULL: "24.0"
     steps:
       - uses: actions/checkout@v4
         with:
@@ -41,6 +47,16 @@ jobs:
       - name: Regenerate static HTML
         run: node colvmn/static-gen.js
 
+      - name: Install wasi-sdk
+        run: |
+          mkdir -p "$HOME/wasi-sdk"
+          curl -L -o /tmp/wasi-sdk.tar.gz \
+            "https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-${WASI_SDK_VERSION}/wasi-sdk-${WASI_SDK_FULL}-x86_64-linux.tar.gz"
+          tar -xzf /tmp/wasi-sdk.tar.gz -C "$HOME/wasi-sdk" --strip-components=1
+
+      - name: Build browser WASM (for /repl/ live interpreter)
+        run: make browser WASI_SDK="$HOME/wasi-sdk"
+
       - name: Upload Pages artifact
         uses: actions/upload-pages-artifact@v3
         with:

FAQ/index.html

@@ -17,6 +17,11 @@
       "type": "ContentCards",
       "columns": 2,
       "items": [
+        {
+          "title": "Live Interpreter",
+          "href": "repl/index.html",
+          "subtitle": "Try Io right now — the full VM compiled to WebAssembly, running in your browser."
+        },
         {
           "title": "Documentation",
           "href": "docs/index.html",

Links/index.html

@@ -1,6 +1,8 @@
 // Io VM — Browser WASM loader + WASI shim + JS bridge + REPL logic
 
-const IO_WASM_URL = "io_browser.wasm";
+// Pages outside browser/ can point at the wasm by setting window.IO_WASM_URL
+// before loading this script.
+const IO_WASM_URL = (typeof window !== "undefined" && window.IO_WASM_URL) || "io_browser.wasm";
 
 let wasm = null;    // WebAssembly instance
 let memory = null;  // WASM linear memory

Timeline/index.html

@@ -67,9 +67,15 @@ static void browser_print_callback(void *context, const UArray *ba) {
 	output_append((const char *)UArray_bytes(ba), UArray_size(ba));
 }
 
+// Set when an uncaught exception reaches the top level during an eval.
+// IoState_tryToPerform clears state->errorRaised after reporting, so this
+// flag is the only way do_eval can tell the input failed.
+static int exception_raised = 0;
+
 // Exception callback: capture exception text
 static void browser_exception_callback(void *context, IoObject *coroutine) {
 	(void)context;
+	exception_raised = 1;
 	// Use the default backtrace printing — it goes through printCallback
 	IoCoroutine_rawPrintBackTrace(coroutine);
 }
@@ -138,6 +144,7 @@ static int do_eval(const char *code) {
 
 	output_clear();
 	state->errorRaised = 0;
+	exception_raised = 0;
 
 	IoObject *result = IoState_doCString_(state, code);
 
@@ -147,7 +154,7 @@ static int do_eval(const char *code) {
 		return 2;
 	}
 
-	if (state->errorRaised) {
+	if (state->errorRaised || exception_raised) {
 		return 1;
 	}
 
@@ -175,6 +182,7 @@ static int do_resume_eval(void) {
 	IoObject *coro = state->suspendedCoro;
 	state->suspendedCoro = NULL;
 	state->awaitingJsPromise = 0;
+	exception_raised = 0;
 
 	// Save current coro state
 	IoObject *previousCoro = (IoObject *)state->currentCoroutine;
@@ -207,7 +215,7 @@ static int do_resume_eval(void) {
 	}
 
 	output_clear();
-	if (state->errorRaised) {
+	if (state->errorRaised || exception_raised) {
 		return 1;
 	}