feat(git): Branches & tags panel — rename, branch from any ref, upstream, tags

GET /git/refs lists local branches (upstream, ahead/behind, last commit,
merged, held by a worktree, protected), remote branches grouped by remote
and tags (target, annotated message/tagger/date). New writes in
server/lib/git-refs.js, dispatched from git-ops.js: branch-rename,
branch-upstream (set/unset), tag-create (light/annotated), tag-delete
(confirm), tag-push (one tag to origin, no --tags, no force), and
branch-create with a looked-up from + switch on a clean tree. Every ref is
looked up, never passed through; repo-wide writes are repo-root only
(ESUBDIR) and refused during any operation (EMERGING).

Client: git/BranchManager + TagManager dialog opened from the git bar's
tags icon, en+vi (gitRefs namespace), keyboard navigable.

# Conflicts:
#	CLAUDE.md
#	client/src/components/lanes/LaneGitBar.tsx
#	docs/API.md
#	server/__tests__/lanes-api.test.js
#	server/routes/lanes.js

client/src/components/lanes/git/refUi.ts

@@ -0,0 +1,41 @@
+/**
+ * @file Shared bits of the Branches panel (`BranchManager`, `TagManager`): the
+ * small button and input classes, the write runner's type, and the arrow-key
+ * walk over a list's rows.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+import type { KeyboardEvent } from "react";
+import type { GitRefAction, GitRefBody } from "../../../lib/api";
+
+/** Runs one write; resolves true when it succeeded (the list is then re-read). */
+export type RunRefAction = (
+  action: GitRefAction,
+  body: GitRefBody,
+  done?: string
+) => Promise<boolean>;
+
+export const smallBtn =
+  "inline-flex items-center gap-1 rounded border border-border-light px-1.5 py-0.5 text-[11px] text-fg-secondary transition-colors hover:bg-surface-3 hover:text-fg-primary disabled:cursor-not-allowed disabled:opacity-40";
+export const smallInput =
+  "min-w-0 flex-1 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";
+
+/** Arrow-key walk over the rows of a list (`[data-ref-row]`), Home/End too. */
+export function onListKeys(e: KeyboardEvent<HTMLElement>) {
+  if (!["ArrowDown", "ArrowUp", "Home", "End"].includes(e.key)) return;
+  // Inside a text field the arrows and Home/End move the caret.
+  if ((e.target as HTMLElement).closest("input, textarea, select")) return;
+  const rows = [...e.currentTarget.querySelectorAll<HTMLElement>("[data-ref-row]")];
+  if (!rows.length) return;
+  const at = rows.indexOf(document.activeElement as HTMLElement);
+  const next =
+    e.key === "Home"
+      ? 0
+      : e.key === "End"
+        ? rows.length - 1
+        : e.key === "ArrowDown"
+          ? Math.min(rows.length - 1, at + 1)
+          : Math.max(0, at - 1);
+  e.preventDefault();
+  rows[next]?.focus();
+}