feat(workspace): AI tool per session, one place to start a session, ended sessions open like Claude Desktop

- A session picks its own AI tool: `tool` on POST /api/lanes/:id/start
  (a catalog id, known + enabled, else 400 EBADTOOL/EDISABLED); a resume
  keeps the tool its session ran on (`sessions.tool`). The workspace's
  `lanes.tool` is now only the default.
- The workspace home's prompt box is the one place a session starts. Its
  fields run in order: AI → AI Router (Native or a profile) → Model (the
  tool's own list, or the router's models) → Permission (Claude mode /
  Codex sandbox+approval / catalog bypass) → Effort.
- The pane's run form (RunSetup) is gone: New run, a single pane's exit and
  an empty split pane's New session all go to the home. RunSetup.tsx keeps
  PromptEditor, CwdAutocomplete and ModelPicker (new `choices` prop).
- The tool icon moved from the sidebar's workspace row to each session row
  (right edge, `session.tool`); the split-pane header shows the run's tool.
- An ended session opens in its workspace (`&session=`, SessionReplay.tsx):
  its conversation read-only plus a prompt box; only a SENT message resumes
  it (resumeSessionId + prompt, first free slot). The console is only
  hidden behind it.
- Analyst button beside Files/Changes in the right panel opens
  /sessions/:id for the opened session.
- Gemini CLI ships its own icon (client/public/ai-tools/gemini.svg, from
  zonalogo.com).
- RouterPicker always shows (Native disabled for tools without router
  support); useAiRouters() exported.
- Tests: server start-with-tool cases; SessionReplay, home field order/tool/
  router models, empty pane, Analyst; dropped the cwd-field suites
  (Run.defaultCwd, Workspace.laneCwd). Docs: CLAUDE.md rules, API.md,
  LANES.md, README, ARCHITECTURE, INSTALL.

client/src/components/lanes/WorkspaceRow.tsx

@@ -2,7 +2,7 @@
  * @file WorkspaceRow — one workspace (lane) in the sidebar's workspace list, one
  * line like a Claude Desktop project: a chevron that expands its sessions, the
  * status dot, the name (click opens the workspace, double-click renames,
- * `PATCH /api/lanes/:id {title}`), the tool's icon, and on hover `+` (a new
+ * `PATCH /api/lanes/:id {title}`) and on hover `+` (a new
  * session there) and `⋯` (the row menu, `WorkspaceRowMenu.tsx`, also on
  * right-click). Dragging it, or Alt+↑/↓, reorders the list — a viewer
  * preference kept in localStorage (`laneOrderStorage.ts`), never written to
@@ -14,8 +14,6 @@ import { useState, type MouseEvent } from "react";
 import { useTranslation } from "react-i18next";
 import { ChevronDown, ChevronRight, MoreHorizontal, Plus } from "lucide-react";
 import type { Lane } from "../../lib/types";
-import { useAiTools } from "../../hooks/useAiTools";
-import { AiToolIcon } from "../AiToolIcon";
 
 /** The row's dot: the lane's liveness, plus a running pulse and needs-you. */
 export function workspaceDot(lane: Lane): string {
@@ -61,7 +59,6 @@ export function WorkspaceRow({
   onRenameEnd: (title: string | null) => void;
 }) {
   const { t } = useTranslation("lanes");
-  const tools = useAiTools();
   const [draft, setDraft] = useState("");
   const [dropTarget, setDropTarget] = useState(false);
   const name = workspaceName(lane);
@@ -153,10 +150,6 @@ export function WorkspaceRow({
         >
           <span className={`h-2 w-2 shrink-0 rounded-full ${workspaceDot(lane)}`} />
           <span className="truncate text-[13px] text-fg-primary">{name}</span>
-          <AiToolIcon
-            tool={{ id: lane.tool, label: tools.label(lane.tool) }}
-            className="h-3.5 w-3.5 shrink-0 !p-0 opacity-70"
-          />
         </button>
       )}
       {!renaming && (