initial: HarborForge plugin for Plexum (port of OpenclawPlugin)

Plugin id `harbor-forge` mirrors the OpenClaw counterpart's runtime
surface on top of the Plexum SDK:

  * eager activation — Monitor bridge + Calendar scheduler boot at
    host start, before any agent turn fires
  * monitor bridge: HTTP 127.0.0.1:<monitor_port> serving /telemetry
    + /health for HarborForge.Monitor
  * calendar scheduler: heartbeats <backendUrl>/calendar/agent/
    heartbeat, dispatches returned slots via HostAPI.WakeAgent
    (state-aware queue, depth-1 replace-newest), tracks active slot
    state in-memory, terminal status pushed back to backend
  * 9 harborforge_* tools (status / telemetry / monitor_telemetry /
    calendar_{status,complete,abort,pause,resume} / restart_status)

Key differences from OpenClaw equivalent:
  * api.spawn → HostAPI.WakeAgent (new SDK primitive)
  * api.getAgentStatus → HostAPI.ReadAgentState (existing)
  * --install-monitor / --install-cli not included; Monitor + hf CLI
    deploy via the HangmanLab.Server.T3 docker compose layer

Initial drop. TODO before v1 ship:
  * tool ctx → calling-agent-id: SDK doesn't currently expose; v1
    falls back to a single-active-slot heuristic in
    main.bestEffortAgentID
  * tests for the bridge + scheduler

Makefile

@@ -0,0 +1,28 @@
+VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo dev)
+GO_ENV  := CGO_ENABLED=0
+
+.PHONY: build install clean help
+
+help:
+	@echo "HarborForge.PlexumPlugin build targets:"
+	@echo "  build    - compile binary + bundle manifest into dist/"
+	@echo "  install  - copy binary + manifest into ~/.plexum/plugins/harbor-forge/"
+	@echo "  clean    - rm -rf dist/"
+
+build:
+	mkdir -p dist
+	$(GO_ENV) go build -ldflags="-X main.Version=$(VERSION)" \
+		-o dist/plexum-harborforge-plugin ./cmd/plexum-harborforge-plugin
+	cp manifest.json dist/manifest.json
+	@echo "Built to dist/ (version=$(VERSION))"
+
+install: build
+	mkdir -p ~/.plexum/plugins/harbor-forge
+	cp dist/plexum-harborforge-plugin ~/.plexum/plugins/harbor-forge/
+	cp dist/manifest.json ~/.plexum/plugins/harbor-forge/
+	@echo "Installed to ~/.plexum/plugins/harbor-forge/"
+	@echo "Add to ~/.plexum/plexum.json .plugins.allow: 'harbor-forge'"
+	@echo "Config goes at ~/.plexum/plugins/harbor-forge/config.json (see README)"
+
+clean:
+	rm -rf dist/