feat: persist user (provider, model) selection per notebook in localStorage

When the user picks a provider+model in the inline prompt, remember
that choice across panel close/reopen AND across JupyterLab restarts,
keyed by notebookPath. If the stored provider (or the model under it)
is no longer present in the current providers payload, fall back to
the default (first provider / default[pid] model) - never silently
apply a stale value that would result in an empty or disabled select.

- New module src/components/model_selection.ts with
  loadModelSelection / saveModelSelection / clearModelSelection.
  Best-effort: localStorage may be disabled (private mode), quota
  may be exhausted, value may be corrupt - all failure modes return
  null / no-op rather than throw.
- IOpenCodeInlinePromptOptions gains notebookPath?: string.
- Constructor resolves the initial selection: prefer stored+valid,
  else first provider / default[pid]. providerSelect.change and
  modelSelect.change listeners call _persistSelection() to keep
  storage in sync.
- _rebuildModelSelect now accepts a preferredModelId; if it exists
  in the current provider's models it's used, else the default.
- OpenCodeCellActions._showPrompt passes notebookPath =
  this._context?.notebookPath so the prompt can key the storage.

Tests
-----
- 10 unit tests in model_selection.spec.ts (load/save/clear +
  malformed JSON + per-notebook independence).
- 4 prompt behavior tests in opencode_cell_actions.spec.ts
  (valid stored applied, provider removed -> default, model removed
  -> default, change -> saved).
- 72 frontend jest (was 58), 52 backend pytest (unchanged),
  build green.

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

src/components/opencode_inline_prompt.ts

@@ -30,12 +30,23 @@ import type {
   OpenCodeMessage,
   OpenCodeProvidersResponse
 } from '../types';
+import {
+  loadModelSelection,
+  saveModelSelection
+} from './model_selection';
 
 export interface IOpenCodeInlinePromptOptions {
   onSubmit: (text: string, providerId?: string, modelId?: string) => void;
   onCancel: () => void;
   disabled: boolean;
   providers: OpenCodeProvidersResponse | null;
+  /**
+   * Notebook path used to key the persisted (provider, model) selection
+   * in localStorage. If omitted (or the stored selection is no longer
+   * valid in the current `providers` payload), the prompt falls back
+   * to the default selection (first provider / `default[pid]` model).
+   */
+  notebookPath?: string;
   /**
    * Respond to a `permission.asked` event. Returns a promise that resolves
    * to true on success, false on failure (the prompt updates the UI in
@@ -143,6 +154,12 @@ export class OpenCodeInlinePrompt extends Widget {
     this._providerModels = flat.providers;
     this._defaultMap = flat.defaultMap;
 
+    // Resolve the initial selection: prefer a previously-saved
+    // (providerId, modelId) IF it's still valid in the current
+    // providers payload; otherwise fall back to the default
+    // (first provider / `default[pid]` model).
+    const stored = this._resolveStoredSelection(options.notebookPath);
+
     if (this._providerModels.length > 0) {
       this._providerSelect = document.createElement('select');
       this._providerSelect.className = 'opencode-provider-select';
@@ -152,16 +169,25 @@ export class OpenCodeInlinePrompt extends Widget {
         o.textContent = p.name ? `${p.id} (${p.name})` : p.id;
         this._providerSelect.appendChild(o);
       }
-      this._providerSelect.value = this._providerModels[0].id;
+      this._providerSelect.value = stored
+        ? stored.providerId
+        : this._providerModels[0].id;
       this._providerSelect.addEventListener('change', () => {
         this._rebuildModelSelect(this._providerSelect!.value);
+        this._persistSelection();
       });
     }
 
     if (this._providerModels.length > 0) {
       this._modelSelect = document.createElement('select');
       this._modelSelect.className = 'opencode-model-select';
-      this._rebuildModelSelect(this._providerSelect?.value);
+      this._rebuildModelSelect(
+        this._providerSelect?.value,
+        stored ? stored.modelId : undefined
+      );
+      this._modelSelect.addEventListener('change', () => {
+        this._persistSelection();
+      });
     }
 
     this._textarea = document.createElement('textarea');
@@ -230,7 +256,10 @@ export class OpenCodeInlinePrompt extends Widget {
     this.node.appendChild(actions);
   }
 
-  private _rebuildModelSelect(providerId: string | undefined): void {
+  private _rebuildModelSelect(
+    providerId: string | undefined,
+    preferredModelId?: string
+  ): void {
     if (!this._modelSelect) {
       return;
     }
@@ -258,8 +287,65 @@ export class OpenCodeInlinePrompt extends Widget {
       this._modelSelect.appendChild(o);
     }
     this._modelSelect.disabled = false;
-    this._modelSelect.value =
-      pickDefaultModelId(providerId, provider.models, this._defaultMap) ?? keys[0];
+    // Honor a preferred model (e.g. from a stored selection), but only
+    // if it actually exists in this provider's model list. Otherwise
+    // fall back to the default.
+    if (
+      preferredModelId &&
+      Object.prototype.hasOwnProperty.call(provider.models, preferredModelId)
+    ) {
+      this._modelSelect.value = preferredModelId;
+    } else {
+      this._modelSelect.value =
+        pickDefaultModelId(providerId, provider.models, this._defaultMap) ??
+        keys[0];
+    }
+  }
+
+  /**
+   * Read the stored (providerId, modelId) for this notebook and
+   * validate it against the current providers payload. Returns the
+   * stored selection only when BOTH the provider and the model still
+   * exist; otherwise returns null and the caller uses the default.
+   */
+  private _resolveStoredSelection(
+    notebookPath: string | undefined
+  ): { providerId: string; modelId: string } | null {
+    if (!notebookPath) {
+      return null;
+    }
+    const sel = loadModelSelection(notebookPath);
+    if (!sel) {
+      return null;
+    }
+    const provider = this._providerModels.find(p => p.id === sel.providerId);
+    if (!provider) {
+      // The provider was removed since the user last picked.
+      return null;
+    }
+    if (!Object.prototype.hasOwnProperty.call(provider.models, sel.modelId)) {
+      // The model was removed (or renamed) under a still-valid provider.
+      return null;
+    }
+    return sel;
+  }
+
+  /**
+   * Persist the current (providerSelect.value, modelSelect.value) for
+   * this notebook. No-op if the prompt has no notebookPath, no
+   * selects, or the values are empty.
+   */
+  private _persistSelection(): void {
+    const notebookPath = this._options.notebookPath;
+    if (!notebookPath || !this._providerSelect || !this._modelSelect) {
+      return;
+    }
+    const providerId = this._providerSelect.value;
+    const modelId = this._modelSelect.value;
+    if (!providerId || !modelId) {
+      return;
+    }
+    saveModelSelection(notebookPath, { providerId, modelId });
   }
 
   setDisabled(disabled: boolean): void {