WC3 512 KiB integration (2026-10-22 UTC)

Merged local WC3 work through cb1953038 with remote main bf99a4285 in an isolated checkout, preserving the root's pending brightness and unrelated edits. The only textual merge conflict was the callback ownership census. Retained both review histories and sealed hashes of the combined sources; ownership remains pending. Reviewed the merged host initialization/cache option, Worker retry guard, immutable GL packet transport and ordered readback paths. The browser-shell delta from remote main only forwards expandedWorkerCodeCache before initialization; it adds no callback or context restoration boundary.

Remote Node broker initialization now touches every RPC slot. Updated the shared-GL broker test's mock buffer to include RPC_MAX_SLOTS rather than four slots. This changes test capacity, not runtime behavior.

Validation: full build and full WAT GL encoder parity pass, including 512 KiB pressure dispatch and ordered records. ThreadManager, Worker scheduler (58 checks), concurrent Worker IOCP, page-index layouts, shared GL protocol, renderer lifecycle, software GL producer, Glide and legacy readiness pass. The combined build has layout 7714899180ab402f; it includes remote changes and is not the byte-identical isolated benchmark artifact. No new FPS or native performance claim is made for the integration. The root dev server remains on the previously measured local 512 KiB build, separate from this checkout.