feat: AI Router per session; Settings at the sidebar's foot; shipped tool icons

AI Router is a session's choice, not a workspace's:
- an AI Router select beside the model picker in the workspace home and a
  pane's run form (RouterPicker.tsx; hidden off Claude/Codex or with only
  Native; last pick remembered in agenthub.session.router)
- `router` on POST /api/lanes/:id/start and POST /api/run; Claude gets
  --settings=<data dir>/router-settings/<name>.json (0600, outranks project
  and user settings, key never in argv), Codex -p <name> + key via tmux -e
- dashboard_runs.router; a resume naming none goes back to it
- profile PATCH rewrites the session files, DELETE removes them
- gone: POST /api/lanes/:id/router/apply, LaneRouterRow, the Add-workspace
  router radio, the claude-/codex-home `routers` answers; clearLaneRouters
  takes the old keys out of each workspace's settings.local.json at start

Sidebar: Settings pinned to the foot, the collapse toggle beside it (stacked
on the rail) instead of in the brand's corner.

Icons: shipped SVG marks for claude, codex, openclaw and hermes (a
black/white pair swapped by theme) in client/public/ai-tools/, used by
AiToolIcon before the server's favicon.

client/src/components/settings/ClaudeAgentHubSettings.tsx

@@ -139,14 +139,7 @@ export function ClaudeAgentHubSettings({ onHomeChanged }: { onHomeChanged?: () =
           api.settings.claudeHome.set(p).then((r) => {
             void load();
             onHomeChanged?.();
-            const missing = r.routers?.missing ?? [];
-            return {
-              value: r.claude_home,
-              envOwned: !!r.env_owned,
-              warning: missing.length
-                ? t("claudeHome.routersMissing", { lanes: missing.join(", ") })
-                : null,
-            };
+            return { value: r.claude_home, envOwned: !!r.env_owned };
           })
         }
       />