browser.ts IPC_REGISTRY still captures the data dir at import

Follow-up promised in the #1490 review. The #1477 sweep (landed via #1490) converted the derived-path constants in the server modules to per-call resolution, but `packages/server/browser.ts:13` still freezes `IPC_REGISTRY` at import time from the data dir, so a `PLANNOTATOR_DATA_DIR` set or changed after import leaves the IPC registry pointing at the old location.

Fix shape: resolve the registry path per call (same pattern as the #1490 modules), keeping any needed caching keyed on the resolved path rather than computed once at module scope.