Refactor manifest build and remove src folder assumptions
- Unified entity builder interface: All entity builders now return
EntityBuildResult<T> with both manifests and filePaths
- Always return build result: runManifestBuild now always returns {
manifest, filePaths } instead of null on failure
- Return all entity paths: EntityFilePaths includes paths for all entity
types (application, objects, functions, etc.)
- Remove src folder assumptions: Applications can now have entities at
root level - removed hasSrcFolder checks
- Simplify watchers: Removed entries caching, compute lazily with map()
- Stabilize tests: Replaced flaky console output snapshots with key
message assertions; replaced inline snapshots with array comparisons
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