Dashboard overhaul, compute integration (#814)

- **Frontend dashboard overhaul**: Unified compute/main dashboards into a single shared UI. Added new pages for cache, projects, metrics, sessions, info (build/runtime config, system stats). Added live-update via WebSockets with pause control, sortable detail tables, themed styling. Refactored compute/hub/orchestrator pages into modular JS.
- **HTTP server fixes and stats**: Fixed http.sys local-only fallback when default port is in use, implemented root endpoint redirect for http.sys, fixed Linux/Mac port reuse. Added /stats endpoint exposing HTTP server metrics (bytes transferred, request rates). Added WebSocket stats tracking.
- **OTEL/diagnostics hardening**: Improved OTLP HTTP exporter with better error handling and resilience. Extended diagnostics services configuration.
- **Session management**: Added new sessions service with HTTP endpoints for registering, updating, querying, and removing sessions. Includes session log file support. This is still WIP.
- **CLI subcommand support**: Added support for commands with subcommands in the zen CLI tool, with improved command dispatch.
- **Misc**: Exposed CPU usage/hostname to frontend, fixed JS compact binary float32/float64 decoding, limited projects displayed on front page to 25 sorted by last access, added vscode:// link support.

Also contains some fixes from TSAN analysis.

1 files changed, 47 insertions, 12 deletions

diff --git a/src/zenserver/diag/otlphttp.cpp b/src/zenserver/diag/otlphttp.cpp
index 1434c9331..d6e24cbe3 100644
--- a/src/zenserver/diag/otlphttp.cpp
+++ b/src/zenserver/diag/otlphttp.cpp
@@ -10,11 +10,18 @@
 #include <protozero/buffer_string.hpp>
 #include <protozero/pbf_builder.hpp>
 
+#include <cstdio>
+
 #if ZEN_WITH_OTEL
 
 namespace zen::logging {
 
 //////////////////////////////////////////////////////////////////////////
+//
+// Important note: in general we cannot use ZEN_WARN/ZEN_ERROR etc in this
+// file as it could cause recursive logging calls when we attempt to log
+// errors from the OTLP HTTP client itself.
+//
 
 OtelHttpProtobufSink::OtelHttpProtobufSink(const std::string_view& Uri) : m_OtelHttp(Uri)
 {
@@ -36,14 +43,44 @@ OtelHttpProtobufSink::~OtelHttpProtobufSink()
 }
 
 void
+OtelHttpProtobufSink::CheckPostResult(const HttpClient::Response& Result, const char* Endpoint) noexcept
+{
+	if (!Result.IsSuccess())
+	{
+		uint32_t PrevFailures = m_ConsecutivePostFailures.fetch_add(1);
+		if (PrevFailures < kMaxReportedFailures)
+		{
+			fprintf(stderr, "OtelHttpProtobufSink: %s\n", Result.ErrorMessage(Endpoint).c_str());
+			if (PrevFailures + 1 == kMaxReportedFailures)
+			{
+				fprintf(stderr, "OtelHttpProtobufSink: suppressing further export errors\n");
+			}
+		}
+	}
+	else
+	{
+		m_ConsecutivePostFailures.store(0);
+	}
+}
+
+void
 OtelHttpProtobufSink::RecordSpans(zen::otel::TraceId Trace, std::span<const zen::otel::Span*> Spans)
 {
-	std::string Data = m_Encoder.FormatOtelTrace(Trace, Spans);
+	try
+	{
+		std::string Data = m_Encoder.FormatOtelTrace(Trace, Spans);
+
+		IoBuffer Payload{IoBuffer::Wrap, Data.data(), Data.size()};
+		Payload.SetContentType(ZenContentType::kProtobuf);
 
-	IoBuffer Payload{IoBuffer::Wrap, Data.data(), Data.size()};
-	Payload.SetContentType(ZenContentType::kProtobuf);
+		HttpClient::Response Result = m_OtelHttp.Post("/v1/traces", Payload);
 
-	auto Result = m_OtelHttp.Post("/v1/traces", Payload);
+		CheckPostResult(Result, "POST /v1/traces");
+	}
+	catch (const std::exception& Ex)
+	{
+		fprintf(stderr, "OtelHttpProtobufSink: exception exporting traces: %s\n", Ex.what());
+	}
 }
 
 void
@@ -55,22 +92,20 @@ OtelHttpProtobufSink::TraceRecorder::RecordSpans(zen::otel::TraceId Trace, std::
 void
 OtelHttpProtobufSink::Log(const LogMessage& Msg)
 {
+	try
 	{
 		std::string Data = m_Encoder.FormatOtelProtobuf(Msg);
 
 		IoBuffer Payload{IoBuffer::Wrap, Data.data(), Data.size()};
 		Payload.SetContentType(ZenContentType::kProtobuf);
 
-		auto Result = m_OtelHttp.Post("/v1/logs", Payload);
-	}
+		HttpClient::Response Result = m_OtelHttp.Post("/v1/logs", Payload);
 
+		CheckPostResult(Result, "POST /v1/logs");
+	}
+	catch (const std::exception& Ex)
 	{
-		std::string Data = m_Encoder.FormatOtelMetrics();
-
-		IoBuffer Payload{IoBuffer::Wrap, Data.data(), Data.size()};
-		Payload.SetContentType(ZenContentType::kProtobuf);
-
-		auto Result = m_OtelHttp.Post("/v1/metrics", Payload);
+		fprintf(stderr, "OtelHttpProtobufSink: exception exporting logs: %s\n", Ex.what());
 	}
 }
 void