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 syntax highlight service from Copybara export and
     keep METADATA excluded_files in sync (copy.bara.sky, METADATA).
   • Package runtime.js in static assets filegroup (static/BUILD,
     static/runtime.js).
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).
   • Add WSGI routing unit tests verifying root path dispatch, prefix
     stripping, and 404 handling (server_test.py).
   • Provide offline asset fallback with timeout in index.html when CDN is
     unreachable, preventing redundant secondary requests (static/index.html).
   • Secure and isolate server tool caches to user-scoped temporary directories
     for demo repositories, safely handling filesystem separation between local
     and remote run dirs (profile_plugin.py, tools_cache_test.py).
3. Client Diagnostic & Data Invariants:
   • Register XProfErrorHandler using type narrowing in app_module.ts to log
     full exception messages and interactive stack traces, accompanied by unit
     tests (app_module.ts, app_module_test.ts).
   • Sanitize uninitialized GPU memory pointers ((null), INVALID, nullptr) with
     a constant Set in cleanCellToken and comprehensive unit tests
     (memory_breakdown_table.ts, memory_breakdown_table_test.ts).
   • Extract clampDataTableNumericValues utility for boundary clamping of
     non-finite and negative metrics (chart_utils.ts, chart_utils_test.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).