style(lanes): render the create-readme option as a selectable card

Matches LaneStripCard's selected/unselected treatment and moves the hint
inside the card. Drops the "codex has no slash commands" clause from the
hint — the option is already hidden for a codex lane.

client/src/components/lanes/AddLaneModal.tsx

@@ -408,18 +408,35 @@ export function AddLaneModal({
         </div>
 
         {tool === "claude" && (
-          <div>
-            <label className="flex items-center gap-2 text-xs text-fg-secondary">
-              <input
-                type="checkbox"
-                checked={writeDocs}
-                onChange={(e) => setWriteDocs(e.target.checked)}
-                className="h-3.5 w-3.5 accent-accent"
-              />
-              {t("addLaneWriteDocsLabel")}
-            </label>
-            <p className="mt-1 text-[10px] text-fg-muted">{t("addLaneWriteDocsHint")}</p>
-          </div>
+          <label
+            // Card that lights up when ticked, matching LaneStripCard's
+            // selected/unselected treatment.
+            className={`flex cursor-pointer items-start gap-2.5 rounded-lg border p-3 shadow-sm transition-colors ${
+              writeDocs
+                ? "border-accent bg-accent/10"
+                : "border-border bg-surface-2 hover:border-border-light hover:bg-surface-3"
+            }`}
+          >
+            <input
+              type="checkbox"
+              // The wrapping label also holds the hint, so name the input
+              // itself — otherwise its accessible name is label + hint.
+              aria-label={t("addLaneWriteDocsLabel")}
+              checked={writeDocs}
+              onChange={(e) => setWriteDocs(e.target.checked)}
+              className="mt-0.5 h-3.5 w-3.5 shrink-0 accent-accent"
+            />
+            <span>
+              <span
+                className={`block text-xs font-medium ${writeDocs ? "text-accent" : "text-fg-secondary"}`}
+              >
+                {t("addLaneWriteDocsLabel")}
+              </span>
+              <span className="mt-1 block text-[10px] text-fg-muted">
+                {t("addLaneWriteDocsHint")}
+              </span>
+            </span>
+          </label>
         )}
 
         {mode === "worktree" && branches && (