feat: Argus v0.4 - Flame Graph, CLI Monitor, OTLP Export

[rlaope]

Summary

Argus v0.4 pivots from VT-focused profiler to a lightweight, zero-dependency JVM monitoring tool (JDK 24+ eliminates VT pinning via JEP 491).

New Features

• Flame Graph: Interactive d3-flamegraph visualization from JFR ExecutionSample data with 60s auto-reset window, pause/resume, and server-side reset
• CLI Monitor (argus top): htop-style terminal UI in new argus-cli module — CPU, heap, GC, virtual threads, hot methods, contention. Zero external dependencies
• OTLP Export: Push-based metrics to OpenTelemetry collectors via hand-coded JSON (no SDK). Configurable via -Dargus.otlp.* system properties
• Install Script: One-line curl | bash installer with argus command PATH setup

Bug Fixes

• Fix d3-flamegraph CDN URL (package name d3-flame-graph, not d3-flamegraph)
• Fix demo duration passthrough in Gradle tasks (default 5 minutes)

Files Changed

Category	Details
New module	argus-cli/ (5 Java files + build.gradle.kts)
New classes	FlameGraphAnalyzer, OtlpJsonBuilder, OtlpMetricsExporter
New script	install.sh
Modified	AgentConfig (OTLP config), ArgusServer, ArgusChannelHandler, EventBroadcaster
Frontend	index.html (CDN fix + flame graph UI), app.js (pause/resume/reset), style.css
Docs	README.md (full rewrite: features, install, quick start, config)

Configuration (New)

-Dargus.otlp.enabled=false
-Dargus.otlp.endpoint=http://localhost:4318/v1/metrics
-Dargus.otlp.interval=15000
-Dargus.otlp.headers=
-Dargus.otlp.service.name=argus

Test plan

• ./gradlew build passes (33 tasks, all green)
• Flame graph renders with profiling enabled (-Dargus.profiling.enabled=true)
• CLI connects and displays live metrics from running server
• /flame-graph endpoint returns d3-compatible JSON
• /flame-graph?format=collapsed returns collapsed stack format
• /flame-graph?reset=true clears server data
• Pause/Resume button freezes flame graph updates with timestamp
• install.sh creates wrapper scripts and configures PATH
• OTLP config fields added to AgentConfig with system property parsing

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