Add missing runner context properties (environment, debug, workspace) (#241)

Fixes #78, #121

Adds three missing properties to the runner context:
- runner.environment: The runner environment (github-hosted or self-hosted)
- runner.debug: Set to '1' when step debug logging is enabled via ACTIONS_STEP_DEBUG
- runner.workspace: The runner-specific working directory path for the job

These are documented official properties that were causing false 'Context access might be invalid' warnings.

languageservice/src/context-providers/default.ts

@@ -83,11 +83,14 @@ function getDefaultContext(name: string, workflowContext: WorkflowContext, mode:
 
     case "runner":
       return objectToDictionary({
-        os: "Linux",
         arch: "X64",
+        debug: "1",
+        environment: "github-hosted",
         name: "GitHub Actions 2",
+        os: "Linux",
+        temp: "/home/runner/work/_temp",
         tool_cache: "/opt/hostedtoolcache",
-        temp: "/home/runner/work/_temp"
+        workspace: "/home/runner/work/repo"
       });
 
     case "secrets":