feat: add structured logging with platform DI

Add a structured logger for GitHub Actions and GitLab CI:
- Log levels: debug, info, warn, error, off (via LOG_LEVEL input)
- Context prefixes for tracking async operations (child loggers)
- Collapsible groups (GitHub ::group::, GitLab section_start)
- Color-coded terminal output
- Platform dependency injection (no hardcoded platform checks)
- fatal() method with bug report URL for uncaught errors

Co-authored-by: Claude <[email protected]>

Author: dgellow

action.yml

@@ -37,3 +37,9 @@ inputs:
     description: "If true, renegerate the endpoints in the Stainless config file."
     required: false
     default: "main"
+  log_level:
+    description: >-
+      Log verbosity level. Options: 'debug', 'info', 'warn', 'error', 'off'.
+      Use 'debug' for detailed diagnostic information.
+    required: false
+    default: "info"

build/action.yml

@@ -71,6 +71,12 @@ inputs:
       https://app.stainless.com/docs/reference/config#open-api-config for
       more details.
     required: false
+  log_level:
+    description: >-
+      Log verbosity level. Options: 'debug', 'info', 'warn', 'error', 'off'.
+      Use 'debug' for detailed diagnostic information.
+    required: false
+    default: "info"
 
 outputs:
   outcomes:

checkout-pr-ref/action.yml

@@ -30,3 +30,9 @@ inputs:
       Stainless config for the preview build.
     required: false
     default: ${{ github.event.pull_request.head.sha }}
+  log_level:
+    description: >-
+      Log verbosity level. Options: 'debug', 'info', 'warn', 'error', 'off'.
+      Use 'debug' for detailed diagnostic information.
+    required: false
+    default: "info"