AGR: Switch rule definition syntax from '@' prefix to ';' suffix

[curtisman]

Summary

This PR changes the Action Grammar (AGR) rule definition syntax from using a @ prefix to using a ; suffix as the rule delimiter. The new syntax is cleaner and more conventional, aligning with common grammar formats where statements end with a terminator rather than begin with a sigil.

Before:

@ <Start> = <scheduleEvent> | <findEvents>
@ <scheduleEvent> = 'schedule' $(title:string) 'on' $(date:CalendarDate) -> { actionName: "scheduleEvent", parameters: { title: title, date: date } }

After:

<Start> = <scheduleEvent> | <findEvents>;
<scheduleEvent> = 'schedule' $(title:string) 'on' $(date:CalendarDate) -> { actionName: "scheduleEvent", parameters: { title: title, date: date } };

Note that dynamic grammar cache (the NFA cache) will break, because the grammar stored is textual currently.

Changes

• Parser (grammarRuleParser.ts): Updated to recognize semicolon-terminated rule definitions instead of @-prefixed ones
• Writer (grammarRuleWriter.ts): Updated to emit semicolons at the end of rule definitions
• Schema generator (schemaToGrammarGenerator.ts): Updated all AI prompt examples and CRITICAL SYNTAX RULES to reflect the new format
• All .agr grammar files: Migrated 25+ agent grammar files across browser, calendar, code, desktop, email, image, list, photo, player, video, and weather agents
• VSCode extension (agr.tmLanguage.json): Updated syntax highlighting to match the new grammar
• Test files: Updated all test cases across actionGrammar, agentSdkWrapper, and cache packages
• Documentation: Updated CONFIGURATION_AND_PERSISTENCE.md with new syntax
• Generated registry: Updated generatedSchemaRegistry.json with regenerated grammar content using new syntax

Test plan

• All existing actionGrammar unit tests pass with the new syntax
• Grammar parsing correctly handles semicolon-terminated rules
• Grammar writing emits valid semicolon-terminated rules
• VSCode extension syntax highlighting works for the new format
• AI-generated grammars from schemaToGrammarGenerator use the new syntax
• Round-trip serialization/deserialization of grammars works correctly

🤖 Generated with Claude Code