feat: abstract GitLab/GitHub CLI usage (#10)

- Move resolveRepoPath to lib/utils.ts
- Update all tools to use createProvider() from lib/providers/
- Remove direct imports from lib/gitlab.ts
- Mark lib/gitlab.ts as deprecated
- All tools now work with both GitHub (gh CLI) and GitLab (glab CLI)
- Provider auto-detected from git remote URL

lib/utils.ts

@@ -0,0 +1,13 @@
+/**
+ * Shared utilities for DevClaw.
+ */
+
+/**
+ * Resolve the repo path from projects.json repo field (handles ~/).
+ */
+export function resolveRepoPath(repoField: string): string {
+  if (repoField.startsWith("~/")) {
+    return repoField.replace("~", process.env.HOME ?? "/home/lauren");
+  }
+  return repoField;
+}