refactor(dirs): restructured environment variable access and simplified configuration in test suite

- Refactored environment variable access to use dedicated getter/setter functions in test suite.
- Simplified configuration constants by removing ompConfig dependency and using hardcoded values.
- Introduced module-level caching for agent directory and subdirectory paths to improve performance.
- Added setAgentDir() function to manage agent directory updates and cache invalidation.
- Reorganized dirs.ts with logical section headers and consolidated subdirectory functions using helper utilities.
- Updated directory accessor functions to accept optional agentDir parameter for flexibility.

packages/coding-agent/package.json

@@ -3,10 +3,6 @@
 	"version": "12.0.0",
 	"description": "Coding agent CLI with read, bash, edit, write tools and session management",
 	"type": "module",
-	"ompConfig": {
-		"name": "omp",
-		"configDir": ".omp"
-	},
 	"bin": {
 		"omp": "src/cli.ts"
 	},