fix(custom-model): replace the native confirm() popup with an in-app modal

The llama-swap "this will unload it for session X" warning used a native
browser confirm() popup, which looks out of place next to the rest of the
app's own modals.

Adds #customModelSwapConfirmModal (index.html) with Cancel/Switch-anyway
buttons, styled to match the app. _confirmModelSwap(message) shows it and
returns a promise that resolves true/false the same way confirm() would;
_resolveModelSwapConfirm(proceed) (wired to both buttons and the backdrop
click) settles it. Both llama-swap conflict call sites
(_quickStartWithCustomModelConfirm for the one-shot launch path,
_runCustomModelEntryViaRestart for Claude's restart path) now await this
instead of calling confirm() directly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RqZeHrRS6DYcGcGX2p9EwG

src/web/public/index.html

@@ -927,6 +927,27 @@
       </div>
     </div>
 
+    <!-- Custom Model Endpoint Profiles: llama-swap model-swap confirmation
+         (docs/custom-model-endpoints-plan.md) — replaces a native confirm()
+         popup, shown when switching would unload a model another live
+         session is actively using. See _confirmModelSwap() in session-ui.js. -->
+    <div class="modal" id="customModelSwapConfirmModal">
+      <div class="modal-backdrop" onclick="app._resolveModelSwapConfirm(false)"></div>
+      <div class="modal-content modal-sm">
+        <div class="modal-header">
+          <h3>Switch models?</h3>
+          <button class="modal-close" onclick="app._resolveModelSwapConfirm(false)" aria-label="Cancel">&times;</button>
+        </div>
+        <div class="modal-body">
+          <p class="form-hint" id="customModelSwapConfirmMessage"></p>
+        </div>
+        <div class="modal-footer">
+          <button class="btn-toolbar" onclick="app._resolveModelSwapConfirm(false)">Cancel</button>
+          <button class="btn-toolbar btn-primary" onclick="app._resolveModelSwapConfirm(true)">Switch anyway</button>
+        </div>
+      </div>
+    </div>
+
     <!-- Cron Jobs Modal -->
     <div class="modal" id="cronModal">
       <div class="modal-backdrop" onclick="app.closeCron()"></div>

src/web/public/session-ui.js

@@ -667,6 +667,32 @@ Object.assign(CodemanApp.prototype, {
     this._pendingCustomModelPick = null;
   },
 
+  /**
+   * In-app replacement for a native `confirm()` popup, used specifically for the
+   * llama-swap "this will unload it for session X" warning (both launch paths below) —
+   * a browser-chrome dialog there looked out of place next to the rest of the app's own
+   * modals. Resolves true/false the same way `confirm()` would; `_resolveModelSwapConfirm`
+   * (the modal's own Cancel/Switch-anyway buttons, and its backdrop click) is what settles
+   * the returned promise.
+   */
+  _confirmModelSwap(message) {
+    const modal = document.getElementById('customModelSwapConfirmModal');
+    const messageEl = document.getElementById('customModelSwapConfirmMessage');
+    if (messageEl) messageEl.textContent = message;
+    modal?.classList.add('active');
+    return new Promise((resolve) => {
+      this._resolveModelSwapConfirmPromise = resolve;
+    });
+  },
+
+  /** Called by the modal's Cancel/Switch-anyway buttons and its backdrop click. */
+  _resolveModelSwapConfirm(proceed) {
+    document.getElementById('customModelSwapConfirmModal')?.classList.remove('active');
+    const resolve = this._resolveModelSwapConfirmPromise;
+    this._resolveModelSwapConfirmPromise = null;
+    resolve?.(proceed);
+  },
+
   /** A model row in the picker modal was clicked: close it and launch with that choice. */
   chooseCustomModelAndRun(modelId) {
     const pending = this._pendingCustomModelPick;
@@ -766,7 +792,7 @@ Object.assign(CodemanApp.prototype, {
     if (data?.data?.requiresConfirmation) {
       const { currentlyLoadedModel, affectedSessions } = data.data;
       const names = affectedSessions.map((s) => s.name || s.id).join(', ');
-      const proceed = confirm(
+      const proceed = await this._confirmModelSwap(
         `${names} ${affectedSessions.length === 1 ? 'is' : 'are'} currently using ` +
           `${currentlyLoadedModel} on this endpoint. Switching will unload it for ` +
           `${affectedSessions.length === 1 ? 'that session' : 'those sessions'} too. Continue?`
@@ -850,7 +876,7 @@ Object.assign(CodemanApp.prototype, {
     // call with `confirmed: true` so the route skips the check the second time.
     if (ok && payload?.requiresConfirmation) {
       const names = payload.affectedSessions.map((s) => s.name || s.id).join(', ');
-      const proceed = confirm(
+      const proceed = await this._confirmModelSwap(
         `${names} ${payload.affectedSessions.length === 1 ? 'is' : 'are'} currently using ` +
           `${payload.currentlyLoadedModel} on this endpoint. Switching to ${modelId} will unload it ` +
           `for ${payload.affectedSessions.length === 1 ? 'that session' : 'those sessions'} too. Continue?`

src/web/public/styles.css

@@ -6825,6 +6825,17 @@ body.touch-device .terminal-container .xterm .xterm-helper-textarea {
   min-height: 0;
 }
 
+/* Custom Model Endpoint Profiles: llama-swap model-swap confirmation — replaces a native
+   confirm() popup (docs/custom-model-endpoints-plan.md) so it looks and feels like the
+   rest of the app instead of a browser chrome dialog. */
+#customModelSwapConfirmModal .modal-footer {
+  display: flex;
+  justify-content: flex-end;
+  gap: 0.5rem;
+  padding: 0.75rem 1rem;
+  border-top: 1px solid var(--border-color);
+}
+
 
 /* Mobile Case Picker - Base Styles */
 .mobile-case-picker-sheet {