Set up dev environment + add AGENTS.md Cursor Cloud notes

[shukieshah]

What

Sets up and verifies the Beacon development environment on the Cloud Agent VM and documents non-obvious setup/run caveats for future agents in a new AGENTS.md.

The only code change is the new AGENTS.md. No product code was modified.

Environment setup performed

• Installed Go 1.24.4 at /usr/local/go (the pre-installed go1.22.2 is too old for the go 1.24/1.25 modules). GOTOOLCHAIN=auto auto-fetches Go 1.25 for the collector exporter module.
• Installed TypeScript SDK deps via npm ci in packages/asymptote-sdk-js.
• Installed golangci-lint for the make lint convenience target.
• Update script (via SetupVmEnvironment): npm ci for the SDK, guarded by lockfile existence. The committed .cursor/environment.json (install.sh/start.sh) remains the source of truth for building the beacon/beacon-hooks binaries and is left unchanged.

Verification

Component	Command	Result
cli/beacon	make build, go test ./..., go test -race ./internal/endpoint/..., go vet ./...	Build/vet pass; tests pass except 2 macOS-only tests (CI runs this job on macOS)
cli/beacon-hooks	go test ./...	pass
pkg/asymptoteobserve	go test ./...	pass
collector-builder/exporter/beaconjsonexporter	go test ./...	pass
SDK	npm test, npm run check, npm run build	pass (22 tests)

The two Linux failures (TestConfigureVSCodePreservesSettingsAndDisablesContentCaptureByDefault, TestRollbackReportsCollectorRestartFailure) are hardcoded for macOS paths/behavior; CI runs the Go test job on macos-latest. Documented in AGENTS.md.

Hello-world demo

Built the beacon CLI, wrote a synthetic validation event + a risky-command event, ran beacon scan (detected curl-pipe-to-shell, HIGH), and ran the local beacon endpoint dashboard web app, verifying the UI, event detail modal, and search filtering in the browser.

beacon_dashboard_demo.mp4

Dashboard events list
Event detail modal

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