Add language service support for action.yml files (#275)

- Add validation, completion, hover, and document links for action.yml files
- Implement document type detection to route action.yml to action-specific handlers
- Add expression context for composite actions (inputs, steps, github, runner, etc.)
- Add schema validation for required fields, branding, and composite step requirements
- Support JavaScript (node20/node24), Docker, and composite action types
- Validate action references in composite action uses steps
- Add JSDoc comments to parser and template functions
- Refactor hover to use hoverToken consistently
- Fix lint errors and add return type annotations

workflow-parser/src/templates/template-parse-result.ts

@@ -0,0 +1,10 @@
+import {TemplateContext} from "./template-context.js";
+import {TemplateToken} from "./tokens/template-token.js";
+
+/**
+ * Result of parsing a template file (workflow or action)
+ */
+export interface TemplateParseResult {
+  context: TemplateContext;
+  value: TemplateToken | undefined;
+}