Resolve open frontend, routing, and packaging defects in OpenXLA XProf:

[copybara-service]

Resolve open frontend, routing, and packaging defects in OpenXLA XProf:

1. Build & Packaging Integrity:
   • Exclude unexported internal syntax highlight service from Copybara export (copy.bara.sky).
2. Server & Routing Contract:
   • Route runtime.js and return HTTP 404 for unmapped endpoints to prevent catch-all HTML masking (server.py, profile_plugin.py, runtime.js).
   • Provide offline asset fallback with timeout in index.html when CDN is unreachable.
   • Prevent server tool caches from polluting tracked repository directories (profile_plugin.py).
3. Client Diagnostic & Data Invariants:
   • Register XProfErrorHandler in app_module.ts to log full exception messages and stack traces.
   • Sanitize uninitialized GPU memory pointers ((null), INVALID) in memory breakdown tables (memory_breakdown_table.ts).
   • Clamp non-finite (NaN) values to 0 in SVG step time graph geometry (step_time_graph.ts).
   • Clamp host/device synchronization self-time skew to prevent negative step durations in input pipeline analyzer (xplane_to_step_events.cc, device_side_analysis_detail_data_provider.ts).