feat(ui): add Git Changes tab

Adds repo-wide git changes view with refresh controls and keeps right drawer shortcuts fixed while tabs scroll.

packages/ui/src/lib/i18n/messages/en/instance.ts

@@ -86,10 +86,12 @@ export const instanceMessages = {
   "instanceShell.empty.description": "Select a session to view messages",
 
   "instanceShell.rightPanel.title": "Status Panel",
-  "instanceShell.rightPanel.tabs.changes": "Changes",
+  "instanceShell.rightPanel.tabs.changes": "Session Changes",
+  "instanceShell.rightPanel.tabs.gitChanges": "Git Changes",
   "instanceShell.rightPanel.tabs.files": "Files",
   "instanceShell.rightPanel.tabs.status": "Status",
   "instanceShell.rightPanel.tabs.ariaLabel": "Right panel tabs",
+  "instanceShell.rightPanel.actions.refresh": "Refresh",
   "instanceShell.rightPanel.sections.sessionChanges": "Session Changes",
   "instanceShell.rightPanel.sections.plan": "Plan",
   "instanceShell.rightPanel.sections.backgroundProcesses": "Background Shells",

packages/ui/src/lib/unified-diff-reverse.ts

@@ -0,0 +1,86 @@
+import { applyPatch, parsePatch } from "diff"
+
+type ParsedPatchIndex = ReturnType<typeof parsePatch>[number]
+type ParsedHunk = ParsedPatchIndex["hunks"][number]
+
+type SdkPatch = {
+  oldFileName: string
+  newFileName: string
+  oldHeader?: string
+  newHeader?: string
+  hunks: Array<{
+    oldStart: number
+    oldLines: number
+    newStart: number
+    newLines: number
+    lines: Array<string>
+  }>
+  index?: string
+}
+
+function invertPatchLine(line: string): string {
+  if (!line) return line
+  const op = line[0]
+  if (op === "+") return `-${line.slice(1)}`
+  if (op === "-") return `+${line.slice(1)}`
+  return line
+}
+
+function reverseParsedHunk(hunk: ParsedHunk): ParsedHunk {
+  return {
+    oldStart: hunk.newStart,
+    oldLines: hunk.newLines,
+    newStart: hunk.oldStart,
+    newLines: hunk.oldLines,
+    lines: hunk.lines.map(invertPatchLine),
+    linedelimiters: Array.isArray((hunk as any).linedelimiters) ? (hunk as any).linedelimiters : [],
+  } as ParsedHunk
+}
+
+function reverseParsedIndex(index: ParsedPatchIndex): ParsedPatchIndex {
+  const hunks = Array.isArray(index.hunks) ? index.hunks : []
+  return {
+    ...index,
+    oldFileName: (index as any).newFileName,
+    newFileName: (index as any).oldFileName,
+    oldHeader: (index as any).newHeader,
+    newHeader: (index as any).oldHeader,
+    hunks: hunks.map(reverseParsedHunk),
+  } as ParsedPatchIndex
+}
+
+export function buildUnifiedDiffFromSdkPatch(patch: SdkPatch): string {
+  const oldName = patch.oldFileName || "a/file"
+  const newName = patch.newFileName || "b/file"
+  const oldHeader = patch.oldHeader ? `\t${patch.oldHeader}` : ""
+  const newHeader = patch.newHeader ? `\t${patch.newHeader}` : ""
+
+  const lines: string[] = []
+  if (patch.index) {
+    // jsdiff can parse arbitrary metadata lines before file headers.
+    lines.push(`Index: ${patch.index}`)
+  }
+  lines.push(`--- ${oldName}${oldHeader}`)
+  lines.push(`+++ ${newName}${newHeader}`)
+  for (const hunk of patch.hunks || []) {
+    const oldRange = hunk.oldLines === 1 ? `${hunk.oldStart}` : `${hunk.oldStart},${hunk.oldLines}`
+    const newRange = hunk.newLines === 1 ? `${hunk.newStart}` : `${hunk.newStart},${hunk.newLines}`
+    lines.push(`@@ -${oldRange} +${newRange} @@`)
+    for (const line of hunk.lines || []) {
+      lines.push(line)
+    }
+  }
+  return `${lines.join("\n")}\n`
+}
+
+export function tryReverseApplyUnifiedDiff(afterText: string, diffText: string): string | null {
+  const normalized = (diffText ?? "").trim()
+  if (!normalized) return null
+
+  const parsed = parsePatch(diffText)
+  if (!Array.isArray(parsed) || parsed.length === 0) return null
+
+  const reversed = reverseParsedIndex(parsed[0])
+  const result = applyPatch(afterText ?? "", reversed)
+  return typeof result === "string" ? result : null
+}