fix(coding-agent): handle force-pushed git extensions in pi update

packages/coding-agent/src/core/package-manager.ts

@@ -935,13 +935,67 @@ export class DefaultPackageManager implements PackageManager {
 			await this.installGit(source, scope);
 			return;
 		}
-		await this.runCommand("git", ["pull"], { cwd: targetDir });
+
+		// Fetch latest from remote (handles force-push by getting new history)
+		await this.runCommand("git", ["fetch", "--prune", "origin"], { cwd: targetDir });
+
+		// Detect default branch and reset to it
+		const defaultBranch = this.getGitDefaultBranch(targetDir);
+		await this.runCommand("git", ["reset", "--hard", `origin/${defaultBranch}`], { cwd: targetDir });
+
+		// Clean untracked files (extensions should be pristine)
+		await this.runCommand("git", ["clean", "-fdx"], { cwd: targetDir });
+
 		const packageJsonPath = join(targetDir, "package.json");
 		if (existsSync(packageJsonPath)) {
 			await this.runCommand("npm", ["install"], { cwd: targetDir });
 		}
 	}
 
+	/**
+	 * Detect the default branch of a git repository.
+	 * Tries multiple methods with fallbacks.
+	 */
+	private getGitDefaultBranch(repoDir: string): string {
+		// Try symbolic-ref first (fast and reliable)
+		const symbolicRef = spawnSync("git", ["symbolic-ref", "-q", "refs/remotes/origin/HEAD"], {
+			cwd: repoDir,
+			encoding: "utf-8",
+		});
+		if (symbolicRef.status === 0 && symbolicRef.stdout) {
+			// Returns something like "refs/remotes/origin/main"
+			const match = symbolicRef.stdout.trim().match(/refs\/remotes\/origin\/(.+)/);
+			if (match) {
+				return match[1];
+			}
+		}
+
+		// Try common branch names
+		for (const branch of ["main", "master"]) {
+			const showRef = spawnSync("git", ["show-ref", "--verify", `refs/remotes/origin/${branch}`], {
+				cwd: repoDir,
+				encoding: "utf-8",
+			});
+			if (showRef.status === 0) {
+				return branch;
+			}
+		}
+
+		// Last resort: use current branch
+		const revParse = spawnSync("git", ["rev-parse", "--abbrev-ref", "HEAD"], {
+			cwd: repoDir,
+			encoding: "utf-8",
+		});
+		if (revParse.status === 0 && revParse.stdout) {
+			const branch = revParse.stdout.trim();
+			if (branch && branch !== "HEAD") {
+				return branch;
+			}
+		}
+
+		return "main";
+	}
+
 	private async removeGit(source: GitSource, scope: SourceScope): Promise<void> {
 		const targetDir = this.getGitInstallPath(source, scope);
 		if (!existsSync(targetDir)) return;