Migrate the build onto lwpt build

[frostney]

Summary

Migrate the project build system onto lwpt build (Path A toolchain adoption).

Why

GocciaScript is lwpt's named first consumer, committed to full toolchain migration. Moving the build onto lwpt build dedups bespoke build logic and aligns with the shared toolchain.

Current behavior

The project builds via its own build.pas targets.

Expected behavior

• Manifest-driven lwpt build produces all current targets, gated behind proven equivalence with the existing build.

Scope notes

• Scheduled after the performance and conformance work. Part of the lwpt migration (parent Migrate toolchain to lwpt #826).