feat(git): search box for the branch switcher (#88)

A Search branches… box beside Switch branch narrows the local and remote
lists to names containing the text (case-insensitive). One match is
picked at once, Enter picks the first, Esc clears. The picked branch
stays listed, so the select never loses its value.

Closes #88

client/src/components/lanes/LaneGitBar.tsx

@@ -132,6 +132,8 @@ export function LaneGitBar({
   const [remoteBranches, setRemoteBranches] = useState<string[]>([]);
   const [worktrees, setWorktrees] = useState<LaneWorktree[]>([]);
   const [picked, setPicked] = useState("");
+  // Issue #88: typing narrows the switcher to the branches whose name holds it.
+  const [branchQuery, setBranchQuery] = useState("");
   const [newBranch, setNewBranch] = useState("");
   // Set when git needed a login for `action`; the form resends that action.
   const [login, setLogin] = useState<{ action: Action; auth: GitAuthNeeded } | null>(null);
@@ -160,6 +162,7 @@ export function LaneGitBar({
     setRemoteBranches([]);
     setWorktrees([]);
     setPicked("");
+    setBranchQuery("");
     setNewBranch("");
     setLogin(null);
     setPassword("");
@@ -176,6 +179,26 @@ export function LaneGitBar({
   // A remote branch: switching creates its local tracking branch; it cannot
   // be deleted here or given a sibling worktree before that.
   const pickedRemote = remoteBranches.includes(picked);
+  // The switcher's lists, narrowed by the search box (case-insensitive, any
+  // part of the name). The picked branch always stays in its list, so the
+  // select never shows a value it has no option for.
+  const query = branchQuery.trim().toLowerCase();
+  const matches = (b: string) => !query || b.toLowerCase().includes(query) || b === picked;
+  const shownBranches = (branches || []).filter(matches);
+  const shownRemote = remoteBranches.filter(matches);
+  const matchCount = query
+    ? [...(branches || []), ...remoteBranches].filter((b) => b.toLowerCase().includes(query))
+        .length
+    : null;
+  const searchBranches = (text: string) => {
+    setBranchQuery(text);
+    const q = text.trim().toLowerCase();
+    if (!q) return;
+    const hits = [...(branches || []), ...remoteBranches].filter((b) =>
+      b.toLowerCase().includes(q)
+    );
+    if (hits.length === 1) setPicked(hits[0]!);
+  };
   const merging = !!git.merging;
 
   const run = async (action: Action, body?: RunBody) => {
@@ -526,6 +549,27 @@ export function LaneGitBar({
 
       {switching && (
         <div className="flex flex-wrap items-center gap-1.5">
+          <input
+            type="search"
+            aria-label={t("gitBar.branchSearch")}
+            placeholder={t("gitBar.branchSearch")}
+            value={branchQuery}
+            disabled={!!busy}
+            onChange={(e) => searchBranches(e.target.value)}
+            onKeyDown={(e) => {
+              if (e.key === "Escape" && branchQuery) {
+                e.stopPropagation();
+                setBranchQuery("");
+              } else if (isSubmitEnter(e)) {
+                e.preventDefault();
+                const first = [...shownBranches, ...shownRemote].find(
+                  (b) => b.toLowerCase().includes(query) && b !== git.branch
+                );
+                if (first) setPicked(first);
+              }
+            }}
+            className="w-36 rounded border border-border-light bg-surface-0 px-2 py-0.5 font-mono text-[11px] text-fg-primary placeholder:text-fg-muted focus:border-accent focus:outline-none"
+          />
           <select
             aria-label={t("gitBar.switchLabel")}
             value={picked}
@@ -533,8 +577,12 @@ export function LaneGitBar({
             onChange={(e) => setPicked(e.target.value)}
             className="select min-w-[8rem] flex-1 !rounded !py-0.5 !pl-2 !pr-6 font-mono !text-[11px]"
           >
-            <option value="">{t("gitBar.switchLabel")}</option>
-            {(branches || []).map((b) => {
+            <option value="">
+              {matchCount === null
+                ? t("gitBar.switchLabel")
+                : t("gitBar.branchMatches", { count: matchCount })}
+            </option>
+            {shownBranches.map((b) => {
               const held = heldBy.get(b);
               return (
                 <option key={b} value={b}>
@@ -543,9 +591,9 @@ export function LaneGitBar({
                 </option>
               );
             })}
-            {remoteBranches.length > 0 && (
+            {shownRemote.length > 0 && (
               <optgroup label={t("gitBar.remoteBranches")}>
-                {remoteBranches.map((b) => (
+                {shownRemote.map((b) => (
                   <option key={`remote:${b}`} value={b}>
                     {b}
                   </option>

client/src/components/lanes/__tests__/LaneGitBar.test.tsx

@@ -337,6 +337,47 @@ describe("LaneGitBar", () => {
     await waitFor(() => expect(api.lanes.gitBranches).toHaveBeenCalledTimes(2));
   });
 
+  it("narrows the branch list as you type, picks a single match and Enter's first one (#88)", async () => {
+    vi.mocked(api.lanes.gitBranches).mockResolvedValue({
+      available: true,
+      branches: ["development", "feat/campaign-pause", "fix/campaign-step", "main"],
+      remotes: ["origin/feat/campaign-statistic", "origin/feature/thienpt/unit_test"],
+      current: "development",
+      worktrees: [],
+    });
+    const user = userEvent.setup();
+    render(<LaneGitBar laneId={3} git={facts({ dirty: 0, untracked: 0 })} onChanged={vi.fn()} />);
+    await user.click(screen.getByRole("button", { name: /Branch/ }));
+    const select = await screen.findByLabelText("Switch branch…");
+    const search = screen.getByLabelText("Search branches…");
+    const options = () =>
+      Array.from(select.querySelectorAll("option"))
+        .map((o) => o.value)
+        .filter(Boolean);
+
+    await user.type(search, "CAMPAIGN");
+    expect(options()).toEqual([
+      "feat/campaign-pause",
+      "fix/campaign-step",
+      "origin/feat/campaign-statistic",
+    ]);
+    expect(select.querySelector("option")).toHaveTextContent("3 matching branches");
+    expect(select).toHaveValue("");
+
+    await user.keyboard("{Enter}");
+    expect(select).toHaveValue("feat/campaign-pause");
+
+    await user.clear(search);
+    await user.type(search, "unit_t");
+    // One match: picked at once (the earlier pick stays listed until replaced).
+    expect(select).toHaveValue("origin/feature/thienpt/unit_test");
+    expect(options()).toEqual(["origin/feature/thienpt/unit_test"]);
+
+    await user.keyboard("{Escape}");
+    expect(search).toHaveValue("");
+    expect(options()).toHaveLength(6);
+  });
+
   it("lists branches only the remote has, switches to one, and re-reads the list after a fetch", async () => {
     vi.mocked(api.lanes.gitBranches).mockResolvedValue({
       available: true,