Add ES6-style shorthand property syntax for grammar object literals

[curtisman]

Summary

This PR implements JavaScript-style shorthand property syntax for object literals in .agr grammar files. When a property name matches a variable name, you can now write { name } instead of the more verbose { name: name }.

Example transformation:

- play $(track:string) -> { actionName: "play", parameters: { track: track } }
+ play $(track:string) -> { actionName: "play", parameters: { track } }

Changes

• Parser (grammarRuleParser.ts): Extended object property parsing to recognize shorthand syntax, storing it as null in the AST to distinguish from explicit values
• Compiler (grammarCompiler.ts): Added validation for shorthand variable references to ensure referenced variables exist in scope
• Matcher (grammarMatcher.ts): Implemented shorthand property resolution during pattern matching
• Writer (grammarRuleWriter.ts): Updated serialization to output shorthand form when appropriate
• Environment (environment.ts): Added parseObjectProperties helper to process shorthand properties in value expressions
• Grammar files: Updated all .agr schema files across agents (browser, calendar, desktop, list, player) to use shorthand syntax
• Tests: Updated all test files to use and verify shorthand syntax

Benefits

• Improved readability: Reduces visual noise in grammar definitions
• Less verbosity: Particularly beneficial for parameter blocks with multiple variables
• Familiar syntax: Aligns with ES6 JavaScript conventions, making grammars more intuitive for developers
• Backward compatible: Full form ({ name: name }) still works; this is purely additive

Test Plan

• ✅ All existing tests pass with updated syntax
• ✅ Parser correctly handles both shorthand and full forms
• ✅ Compiler validates shorthand variable references
• ✅ Matcher resolves shorthand properties correctly
• ✅ Serialization round-trips preserve shorthand form

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