Add GitHub integration for PRs, issues and AI PR description (#205)

* feat: integrate GitHub OAuth device flow across runtimes

Add GitHub OAuth device flow endpoints across runtimes
Introduce GitHubSettings UI panel and sidebar entry
Persist GitHub auth state in per-runtime storage

* feat: add GitHub PR status and PR description generation

Show PR status for the current branch in the Git view
Generate a pull request description from the diff between base and head
Expose prStatus, prCreate, and prMerge APIs in web and desktop clients

* feat: add GitHub PR ready for review

Add API to mark pull requests as ready for review
Show a Ready button for draft PRs and reflect status in UI
Handle token expiration and GraphQL errors when marking ready

packages/vscode/src/gitService.ts

@@ -684,6 +684,48 @@ export async function getGitDiff(
   return { diff: result.stdout };
 }
 
+/**
+ * Get diff between two refs for a file (base...head).
+ */
+export async function getGitRangeDiff(
+  directory: string,
+  base: string,
+  head: string,
+  filePath: string,
+  contextLines = 3
+): Promise<{ diff: string }> {
+  const baseRef = (base || '').trim();
+  const headRef = (head || '').trim();
+  if (!baseRef || !headRef) {
+    return { diff: '' };
+  }
+  const args = ['diff', '--no-color', `-U${Math.max(0, contextLines)}`, `${baseRef}...${headRef}`, '--', filePath];
+  const result = await execGit(args, directory);
+  return { diff: result.stdout };
+}
+
+/**
+ * List files changed between two refs (base...head).
+ */
+export async function getGitRangeFiles(
+  directory: string,
+  base: string,
+  head: string
+): Promise<string[]> {
+  const baseRef = (base || '').trim();
+  const headRef = (head || '').trim();
+  if (!baseRef || !headRef) {
+    return [];
+  }
+  const args = ['diff', '--name-only', `${baseRef}...${headRef}`];
+  const result = await execGit(args, directory);
+  if (result.exitCode !== 0) return [];
+  return String(result.stdout || '')
+    .split('\n')
+    .map((l) => l.trim())
+    .filter(Boolean);
+}
+
 /**
  * Get file diff with original and modified content
  */