* Update LocalModelsUpdater to support dense model files
Add Observer pattern to LocalModelsUpdaterState for notifying
consumers when models are ready. Add dense model file paths for
the 2_Dense and 3_Dense layers.
* Add model loading to LocalAIService and WASM bridge
* Add model loading tests for LocalAIService
Add branch-3-specific tests for the 3-way readiness model
(WASM page loaded, component ready, mojo remote bound).
Fix SetInstallDir to handle empty path as reset for test isolation.
* Read model files directly into BigBuffer shared memory
Allocate BigBuffer(size) upfront — for files >64KB this uses shared
memory internally — then read the file directly into its storage
via File::ReadAndCheck, avoiding a separate heap allocation.
Replace TryLoadModel boolean flags with BarrierClosure(2) that
fires LoadLocalModelFiles once both conditions are met: component
models delivered and WASM factory registered. A fresh barrier is
created on each reset.
Use dependency injection for LocalModelsUpdaterState instead of
GetInstance() singleton access.
Anthony Tseng
80c9469f1d