fix: add retry logic for npm install to handle transient registry failures

Add retry logic with exponential backoff (5s, 10s, 20s) to handle transient
NPM registry failures like 503 Service Unavailable errors.

This prevents build failures when npmjs.org has temporary outages, which
can happen during CI runs.

Features:
- 3 retry attempts with exponential backoff
- Detailed logging of retry attempts
- Only fails after all retries exhausted

Fixes the Production Readiness CI failure seen at:
https://github.com/pulseengine/rules_wasm_component/actions/runs/19322218044

Author: avrabe

toolchains/jco_toolchain.bzl

@@ -200,19 +200,43 @@ def _setup_downloaded_jco_tools(repository_ctx, platform, jco_version, node_vers
 
     print("JCO dependencies configured")
 
-    # Actually install the packages using npm
-    npm_install_result = repository_ctx.execute([
-        str(npm_binary),
-        "install",
-        "--global-style",
-        "--no-package-lock",
-    ] + install_packages, environment = npm_env, working_directory = "jco_workspace")
+    # Install packages with retry logic for transient registry failures
+    max_retries = 3
+    retry_delay_seconds = 5
+    npm_install_result = None
+
+    for attempt in range(1, max_retries + 1):
+        if attempt > 1:
+            print("Retrying npm install (attempt {}/{}) after {}s delay...".format(
+                attempt, max_retries, retry_delay_seconds
+            ))
+            # Simple delay using execute with sleep
+            repository_ctx.execute(["sleep", str(retry_delay_seconds)])
+            retry_delay_seconds *= 2  # Exponential backoff
+
+        npm_install_result = repository_ctx.execute([
+            str(npm_binary),
+            "install",
+            "--global-style",
+            "--no-package-lock",
+        ] + install_packages, environment = npm_env, working_directory = "jco_workspace")
+
+        if npm_install_result.return_code == 0:
+            break
+
+        print("npm install attempt {} failed (return code: {})".format(
+            attempt, npm_install_result.return_code
+        ))
+        if attempt < max_retries:
+            print("STDERR:", npm_install_result.stderr)
 
     if npm_install_result.return_code != 0:
-        print("ERROR: npm install failed:")
+        print("ERROR: npm install failed after {} attempts:".format(max_retries))
         print("STDOUT:", npm_install_result.stdout)
         print("STDERR:", npm_install_result.stderr)
-        fail("Failed to install jco dependencies: {}".format(npm_install_result.stderr))
+        fail("Failed to install jco dependencies after {} retries: {}".format(
+            max_retries, npm_install_result.stderr
+        ))
 
     print("JCO installation completed successfully")