feat(lanes,ui): per-lane git surface — Changes panel, VS Code-style diff, branch-aware Add lane, redesigned tooltips (#34, #35)

- Changes card beside lane detail with five modes: Files tree, overview,
  Review (whole diff, per-file collapse), single file, commit history.
- LaneDiffView: unified / side-by-side with independent scroll on both axes
  and mirrored scrollLeft, expand/collapse context, intra-line emphasis.
- Staged-only commit box; git actions (fetch/pull/push/stage/unstage/
  discard/commit/switch/branch-create/branch-delete) guarded in git-ops.js.
- Server: git-diff.js + git-ops.js behind GET /api/lanes/:id/git/* and
  POST /api/lanes/:id/git/:action; gitFacts gains upstream/ahead/behind.
- Add lane: new/existing branch, current branch, worktree list, prefill
  from the git bar's "New lane here"; /api/run/cwds gains a repo kind.
- GlobalTooltip upgrades every native title into a themed anchored bubble;
  chart/info popovers use theme tokens.

client/src/components/workflows/OrchestrationDAG.tsx

@@ -853,7 +853,7 @@ export function OrchestrationDAG({ data, onNodeClick, selectedNode }: Orchestrat
         ref={tipRef}
         role="tooltip"
         aria-hidden="true"
-        className="fixed z-50 px-3 py-2 bg-[#12121f] border border-[#2a2a4a] rounded-lg shadow-2xl pointer-events-none"
+        className="fixed z-50 px-3 py-2 bg-surface-2 border border-border rounded-lg shadow-2xl pointer-events-none"
         style={{
           display: "none",
           opacity: 0,
@@ -922,10 +922,11 @@ function buildDAGTooltipContent(el: HTMLDivElement, node: DAGNode, t: TFn) {
     row.style.cssText =
       "display:flex;justify-content:space-between;gap:16px;font-size:11px;line-height:1.6";
     const lbl = document.createElement("span");
-    lbl.style.color = "#64748b";
+    lbl.style.color = "rgb(var(--fg-muted))";
     lbl.textContent = label;
     const val = document.createElement("span");
-    val.style.cssText = "color:#cbd5e1;font-weight:500;font-variant-numeric:tabular-nums";
+    val.style.cssText =
+      "color:rgb(var(--fg-primary));font-weight:500;font-variant-numeric:tabular-nums";
     val.textContent = value;
     row.appendChild(lbl);
     row.appendChild(val);
@@ -935,12 +936,12 @@ function buildDAGTooltipContent(el: HTMLDivElement, node: DAGNode, t: TFn) {
 
   const desc = document.createElement("p");
   desc.style.cssText =
-    "font-size:11px;color:#94a3b8;line-height:1.45;border-top:1px solid #2a2a4a;padding-top:8px;margin:0";
+    "font-size:11px;color:rgb(var(--fg-secondary));line-height:1.45;border-top:1px solid rgb(var(--border));padding-top:8px;margin:0";
   desc.textContent = meta.description;
   el.appendChild(desc);
 
   const hint = document.createElement("p");
-  hint.style.cssText = "font-size:10px;color:#64748b;line-height:1.45;margin:6px 0 0";
+  hint.style.cssText = "font-size:10px;color:rgb(var(--fg-muted));line-height:1.45;margin:6px 0 0";
   hint.textContent = t("orchestration.tooltip.tipClickToFilter");
   el.appendChild(hint);
 }