refactor(locale): move hardcoded UI strings into english locale

Adds optional namespaces (common, errors, commandPalette, headTitle,
notifications, schedule, events, home, reader, routes, badgePreview,
badgeWall) and extends existing ones (settings.*, lists.*, tools.*,
user.*, hololive.*) on the Locale interface. New fields are optional
so japanese.ts can omit them; svelte-i18n's fallbackLocale handles
the runtime miss.

HeadTitle gains an optional routeKey prop for type-safe lookup.
defaultActions becomes a factory so the command palette re-reads
locale on language toggle. The existing JP feedback translation
in routes/settings is preserved via japanese.ts.

Out of scope (kept hardcoded): service-worker.ts, app.html,
Landing*.svelte, tools.ts registry, Easter Event 2025 pages.

1 files changed, 4 insertions, 3 deletions

diff --git a/src/routes/tools/[tool]/+page.svelte b/src/routes/tools/[tool]/+page.svelte
index ff764add..b74952a5 100644
--- a/src/routes/tools/[tool]/+page.svelte
+++ b/src/routes/tools/[tool]/+page.svelte
@@ -20,6 +20,7 @@ import Popup from "$lib/Layout/Popup.svelte";
 import SequelCatcher from "$lib/Tools/SequelCatcher/Tool.svelte";
 import Tracker from "$lib/Tools/Tracker/Tool.svelte";
 import BirthdaysTemplate from "$lib/Tools/BirthdaysTemplate.svelte";
+import locale from "$stores/locale";
 import type { PageData } from "./$types";
 
 export let data: PageData;
@@ -38,15 +39,15 @@ $: if (tool === "girls") goto(root("/girls"));
 <Picker bind:tool />
 
 {#if !Object.keys(tools).includes(tool)}
-  <HeadTitle route="Tools" path="/tools" />
+  <HeadTitle routeKey="tools" path="/tools" />
 
   <Popup>
     <p style="text-align: center;">
-      Tool "<a href={root(`/tools/${tool}`)}>{tool}</a>" not found
+      {$locale().errors?.toolNotFoundPrefix}<a href={root(`/tools/${tool}`)}>{tool}</a>{$locale().errors?.toolNotFoundSuffix}
     </p>
 
     <blockquote style="margin: 0 0 0 1.5rem;">
-      Did you mean "<a
+      {$locale().errors?.didYouMean} "<a
         href={root(`/tools/${tools[suggestion].id}`)}
         onclick={() => (tool = suggestion)}
         style={suggestion === '...' ? 'pointer-events: none; color: inherit;' : ''}