vmsig: management daemon, runtime endpoint lifecycle, roster, discovery, in-tree drivers, packaging

- core: runtime attach/detach of a per-endpoint adapter trio (runtime-safe add_adapter + vmsig_core_detach_endpoint, deferred reap)
- roster: VMSIG_EV_ROSTER + CAP_ROSTER, retained per-endpoint and replayed to late subscribers
- discovery: inotify trigger dir, vmid/endpoint slot allocator, host probe; vmsigd daemon with config + per-uid admission
- input driver and vgpu perception built in-tree; vgpu perception as a separate library
- memctx: own the supplied ro_fd (closed at detach)
- deb packaging: install rules, systemd unit, tmpfiles, default config

Makefile

@@ -0,0 +1,46 @@
+# vmsig packaging — `make deb` builds the .deb over a `cmake --install` stage.
+# Private values are NOT baked into the tree: pass them via the variables below (the
+# defaults are neutral placeholders; CI overrides them from vars/secrets).
+#
+#   make deb LIBVMIE_PATH=/path/to/vmie VERSION=1.2.3 \
+#            MAINTAINER="Name <addr>" DEPENDS="libc6, libvmie0"
+
+VERSION     ?= 0.0.0
+MAINTAINER  ?= vmsig packaging <root@localhost>
+# libvmie0 is vmie's own runtime package (SONAME libvmie.so.0): libvmsig.so and
+# libvgpu-perception.so dynamically link it, so it is a HARD runtime dependency.
+DEPENDS     ?= libc6, libvmie0
+ARCH        ?= amd64
+LIBVMIE_PATH ?=
+
+BUILD_DIR   ?= .build-pkg
+STAGE       ?= $(CURDIR)/dist/stage
+DIST        ?= $(CURDIR)/dist
+
+.PHONY: deb clean
+
+# Armed package: the shipped daemon needs vmie for memctx. vmie stays an external dependency
+# (the package Depends on its runtime; pass DEPENDS to add it).
+deb:
+	@test -n "$(LIBVMIE_PATH)" || { echo "set LIBVMIE_PATH=/path/to/vmie sources (armed memctx)"; exit 1; }
+	rm -rf $(STAGE)
+	cmake -S . -B $(BUILD_DIR) -DCMAKE_BUILD_TYPE=Release -DVMSIG_INSTALL=ON \
+	      -DVMSIG_WITH_VMIE=ON -DLIBVMIE_PATH=$(LIBVMIE_PATH)
+	cmake --build $(BUILD_DIR) -j
+	DESTDIR=$(STAGE) cmake --install $(BUILD_DIR) --prefix /usr
+	mkdir -p $(STAGE)/DEBIAN
+	sed -e 's/@VERSION@/$(VERSION)/' \
+	    -e 's|@MAINTAINER@|$(MAINTAINER)|' \
+	    -e 's/@DEPENDS@/$(DEPENDS)/' \
+	    packaging/deb/control.in > $(STAGE)/DEBIAN/control
+	cp packaging/deb/conffiles $(STAGE)/DEBIAN/conffiles
+	install -m 0755 packaging/deb/postinst $(STAGE)/DEBIAN/postinst
+	install -m 0755 packaging/deb/prerm    $(STAGE)/DEBIAN/prerm
+	# strip inherited setgid from staged dirs (a setgid build tree => dpkg-deb rejects DEBIAN)
+	find $(STAGE) -type d -exec chmod g-s {} +
+	mkdir -p $(DIST)
+	dpkg-deb --root-owner-group --build $(STAGE) $(DIST)/vmsig_$(VERSION)_$(ARCH).deb
+	@echo "built: $(DIST)/vmsig_$(VERSION)_$(ARCH).deb"
+
+clean:
+	rm -rf $(BUILD_DIR) $(DIST)