feat(settings): data-safe editors, deep-linked search, Data/About/Cost pages

- EditorModal loads once per path (a parent re-render no longer reloads the
  file over the user's typing), refuses Save after a failed load, opens a
  truncated (>256 KB) file read-only, and asks before overwriting a file
  that changed on disk or could not be re-read.
- Settings/Hooks editors unset only keys from the snapshot taken at Edit,
  warn when the file changed underneath, keep a renamed key's value, and
  refuse a new key named like a redacted one (env) or a read-only hook
  event, which used to replace the secret/hooks.
- Project scope shows its resolved folder and is disabled inside the
  plugin cache. Account-profile, pricing-row and pet deletes confirm;
  two-click actions disarm after 3 s; unsaved drafts ask before closing.
- Search indexes every Claude Code / Codex sub-tab, opens it via ?tab= and
  scrolls to + highlights the row; the active config tab is in the URL.
- General splits into General / Data / About; Pricing moves to a Cost
  group with one shared load; config tabs group as Content / Extensions /
  Config with arrow-key roving; Promise.allSettled per tab.
- Data: browser-preferences export/import (allowlisted keys), per-section
  reset, housekeeping dry-run first, clear-all behind a typed phrase.
  Server: purge days must be a whole number >= 1 (INVALID_PURGE_DAYS) and
  dry_run returns exactly what the real run would delete.
- Alerts can be edited; webhooks/alerts/remote-source failures toast;
  copies go through copyText; modals get dialog roles and useDialog.
- Sagi: Ctrl/Cmd+B only when shown and not typing, default spot clear of
  row controls, arrow keys move it, reduced motion honoured; the dead
  /run launch link goes to the workspace.

client/src/components/settings/SettingsRow.tsx

@@ -2,25 +2,29 @@
  * @file SettingsRow — the settings page's row primitives: a titled card
  * (`SettingsSection`), a label/description | control row (`SettingsRow`), a
  * switch row (`SettingsSwitchRow`) and a segmented radio group
- * (`SettingsSegmented`). Rows divide themselves with a hairline, none after the
- * last, so a section is just its rows in order.
+ * (`SettingsSegmented`, arrow keys + one roving tab stop). Rows divide
+ * themselves with a hairline, none after the last, so a section is just its
+ * rows in order.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
 import { Switch } from "../Switch";
-import type { ReactNode } from "react";
+import type { KeyboardEvent, ReactNode } from "react";
 
 export function SettingsSection({
+  id,
   title,
   description,
   children,
 }: {
+  /** `<section id>` — a deep-link target. */
+  id?: string;
   title: ReactNode;
   description?: ReactNode;
   children: ReactNode;
 }) {
   return (
-    <section className="card p-5">
+    <section id={id} className={id ? "card p-5 scroll-mt-24" : "card p-5"}>
       <h3 className="text-sm font-semibold text-fg-primary">{title}</h3>
       {description && <p className="mt-0.5 text-xs text-fg-muted">{description}</p>}
       <div className="mt-2">{children}</div>
@@ -87,18 +91,36 @@ export function SettingsSegmented<T extends string>({
   onChange: (v: T) => void;
   ariaLabel?: string;
 }) {
+  // A radio group's keyboard contract: one tab stop (the checked option), and
+  // the arrow keys move the selection — wrapping — and the focus with it.
+  const onKeyDown = (e: KeyboardEvent<HTMLDivElement>) => {
+    const step = { ArrowRight: 1, ArrowDown: 1, ArrowLeft: -1, ArrowUp: -1 }[e.key];
+    if (!step || options.length === 0) return;
+    e.preventDefault();
+    const at = Math.max(
+      0,
+      options.findIndex((o) => o.value === value)
+    );
+    const next = (at + step + options.length) % options.length;
+    onChange(options[next]!.value);
+    (e.currentTarget.children[next] as HTMLElement | undefined)?.focus();
+  };
   return (
     <div
       role="radiogroup"
       aria-label={ariaLabel}
+      onKeyDown={onKeyDown}
       className="inline-flex rounded-lg border border-border bg-surface-2 p-0.5"
     >
-      {options.map((o) => (
+      {options.map((o, i) => (
         <button
           key={o.value}
           type="button"
           role="radio"
           aria-checked={value === o.value}
+          tabIndex={
+            value === o.value || (i === 0 && !options.some((x) => x.value === value)) ? 0 : -1
+          }
           onClick={() => onChange(o.value)}
           className={`flex items-center gap-1.5 rounded-md px-3 py-1.5 text-xs font-medium transition-colors ${
             value === o.value