feat(web): settings form polish — dialog layout, homepage button, no default rows, unified dropdown text (#39)

Co-authored-by: Alice <alice@prismshadow.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/web/src/features/chat/thinking-level.ts

@@ -41,7 +41,7 @@ export function thinkingLevelLabel(
 /** One dropdown row of the agent-settings thinking-level menu (shape of OptionMenuChoice<string>). */
 export interface ThinkingLevelOptionRow {
   value: string;
-  /** Compact text on the trigger button ("" renders the localized default tag). */
+  /** Compact text on the trigger button. */
   triggerLabel: string;
   /** Panel row title. */
   label: string;
@@ -51,25 +51,30 @@ export interface ThinkingLevelOptionRow {
 
 /**
  * Assembles the agent-settings thinking-level dropdown rows from the dictionary's
- * [value, description] pairs (which no longer include `none`). Backward compatibility:
- * when the **persisted** config already stores `none` (a legacy value), a display-only
- * row for it is appended — the trigger shows the real stored state instead of "—" and
- * nothing is silently rewritten. Gating on the persisted value (not the local edit
- * state) means a misclick onto another tier keeps the row until the change is actually
- * saved, so the user can always click back to the value still stored on disk.
+ * [value, description] pairs, composing both review decisions:
+ * - the "" (inherit) row is **filtered** — the menu offers only concrete tiers, the user
+ *   picks explicitly; an unset value shows the OptionMenu's (default) placeholder and the
+ *   reset link next to the menu rewinds a local pick back to it;
+ * - `none` is no longer offered (many models cannot disable thinking) but stays a valid
+ *   stored value: when the **persisted** config already carries it, a display-only row is
+ *   appended — the trigger shows the real stored state and nothing is silently rewritten.
+ *   Gating on the persisted value (not the local edit state) means a misclick onto another
+ *   tier keeps the row until the change is actually saved, so the user can always click
+ *   back to the value still stored on disk.
  */
 export function thinkingLevelOptionsFor(
   options: ReadonlyArray<readonly [string, string]>,
-  defaultTag: string,
   noneKeptDescription: string,
   storedLevel: string | undefined,
 ): ThinkingLevelOptionRow[] {
-  const rows = options.map(([value, description]) => ({
-    value,
-    triggerLabel: value || defaultTag,
-    label: value || defaultTag,
-    description,
-  }));
+  const rows = options
+    .filter(([value]) => value !== "")
+    .map(([value, description]) => ({
+      value,
+      triggerLabel: value,
+      label: value,
+      description,
+    }));
   if (storedLevel === "none") {
     rows.push({
       value: "none",