feat(settings): one page per section with a grouped nav and search

Settings moves from a tab bar to /settings/<section>: a left nav grouped
General / Agents / Routing / Git / Projects (a select on narrow screens), a
search box over every section (Ctrl/Cmd+F, Enter opens the first match), and
row primitives. Each AI tool has its page under agents/<id>, the AI Tools
modal becomes the Agents page, Pricing shows every vendor, Git → Worktrees
sets which untracked worktrees the sidebar lists, and each project gets a
page with its own worktree override and Forget all. ?tool= and #ai-tools
links redirect to the path form.

client/src/pages/AiToolConfig.tsx

@@ -221,7 +221,7 @@ export function AiToolConfig({ toolId }: { toolId: string }) {
               </a>
             )}
             {tool.update && (
-              <Link to={`/settings?tool=${toolId}#ai-tools`} className="btn-ghost text-xs">
+              <Link to="/settings/agents" className="btn-ghost text-xs">
                 <RefreshCw className="h-3.5 w-3.5" />
                 {t("toolTab.update")}
               </Link>