Scaffold core/OBS-adapter split, prove CMake toolchain, add 3-platform CI

First pass on the streamer-tools OBS camera plugin: a minimal but real
CMake project matching the design doc's core-library/OBS-adapter split
(docs/superpowers/specs/2026-09-06-obs-camera-plugin-design.md in the
streamer-tools repo). No LiveKit FFI integration yet -- this proves the
toolchain works.

- core/: dependency-free C++17 library (no OBS dependency), unit tested
  via CTest with no external test framework.
- obs-adapter/: adapted from obsproject/obs-plugintemplate (commit
  3e7d7ac, 2025-12-09). Registers a real, stubbed OBS source type;
  builds as a genuine dynamically-linked OBS module against Ubuntu's
  system libobs-dev (confirmed via ldd/nm, not a fake stand-in).
- Simpler hand-written top-level CMakeLists.txt in place of the
  template's full buildspec-driven bootstrap (which downloads full OBS
  source + prebuilt deps) -- find_package(libobs) alone is enough on
  Linux; falls back to core-library-only when libobs isn't found
  (expected on macOS/Windows CI for now).
- .gitea/workflows/build.yml: 3-platform matrix (ubuntu-latest,
  macos-latest, windows-latest) matching the runners confirmed
  available to this repo under the CyberCoveLLC org.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RL8abRmgFXkVASHkkqiJbE

obs-adapter/CMakeLists.txt

@@ -0,0 +1,37 @@
+# streamer-tools OBS Camera Plugin - OBS adapter
+#
+# Thin glue only, per the design doc: source registration, (eventually)
+# properties UI, and pushing frames into OBS. All real logic lives in
+# ../core. Only added to the build when find_package(libobs) succeeds
+# (see top-level CMakeLists.txt) -- see README.md for why.
+
+set(STPLUGIN_PROJECT_NAME "streamer-tools-camera")
+set(STPLUGIN_PROJECT_VERSION "${PROJECT_VERSION}")
+
+configure_file(
+    src/plugin-support.c.in
+    ${CMAKE_CURRENT_BINARY_DIR}/plugin-support.c
+    @ONLY
+)
+
+add_library(${STPLUGIN_PROJECT_NAME} MODULE
+    src/plugin-main.c
+    ${CMAKE_CURRENT_BINARY_DIR}/plugin-support.c
+)
+
+target_include_directories(${STPLUGIN_PROJECT_NAME}
+    PRIVATE
+        ${CMAKE_CURRENT_SOURCE_DIR}/src
+        ${CMAKE_CURRENT_BINARY_DIR}
+)
+
+target_link_libraries(${STPLUGIN_PROJECT_NAME}
+    PRIVATE
+        OBS::libobs
+        stplugin_core
+)
+
+set_target_properties(${STPLUGIN_PROJECT_NAME} PROPERTIES
+    PREFIX ""
+    OUTPUT_NAME ${STPLUGIN_PROJECT_NAME}
+)

obs-adapter/data/locale/en-US.ini

@@ -0,0 +1,2 @@
+# streamer-tools OBS Camera Plugin - en-US locale
+# No user-facing strings yet -- this is scaffolding (see plugin-main.c).

obs-adapter/src/plugin-main.c

@@ -0,0 +1,74 @@
+/*
+streamer-tools OBS Camera Plugin
+Copyright (C) 2026 CyberCoveLLC <jknapp85@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program. If not, see <https://www.gnu.org/licenses/>
+*/
+
+/* SCAFFOLDING. This registers a source type so the OBS-adapter/core-
+ * library split and OBS's module-loading toolchain can be proven end to
+ * end, but it does not do anything real yet: no LiveKit FFI session, no
+ * frames pushed via obs_source_output_video/audio, no properties UI.
+ * See docs/superpowers/specs/2026-09-06-obs-camera-plugin-design.md in
+ * the streamer-tools repo for what this becomes. */
+
+#include <obs-module.h>
+#include <util/bmem.h>
+#include <plugin-support.h>
+#include <stplugin/core_c.h>
+
+OBS_DECLARE_MODULE()
+OBS_MODULE_USE_DEFAULT_LOCALE(PLUGIN_NAME, "en-US")
+
+static const char *stcam_source_get_name(void *unused)
+{
+	UNUSED_PARAMETER(unused);
+	return "streamer-tools Camera (scaffold - not yet functional)";
+}
+
+static void *stcam_source_create(obs_data_t *settings, obs_source_t *source)
+{
+	UNUSED_PARAMETER(settings);
+	UNUSED_PARAMETER(source);
+	/* No LiveKit session, no state to speak of yet -- just proving the
+	 * source registers and OBS can instantiate/destroy it cleanly. */
+	return bzalloc(1);
+}
+
+static void stcam_source_destroy(void *data)
+{
+	bfree(data);
+}
+
+static struct obs_source_info streamer_tools_camera_source = {
+	.id = "streamer_tools_camera_source",
+	.type = OBS_SOURCE_TYPE_INPUT,
+	.output_flags = OBS_SOURCE_ASYNC_VIDEO,
+	.get_name = stcam_source_get_name,
+	.create = stcam_source_create,
+	.destroy = stcam_source_destroy,
+};
+
+bool obs_module_load(void)
+{
+	obs_log(LOG_INFO, "streamer-tools camera plugin scaffold loaded (core library version %s)",
+		stplugin_core_version());
+	obs_register_source(&streamer_tools_camera_source);
+	return true;
+}
+
+void obs_module_unload(void)
+{
+	obs_log(LOG_INFO, "streamer-tools camera plugin scaffold unloaded");
+}

obs-adapter/src/plugin-support.c.in

@@ -0,0 +1,43 @@
+/*
+streamer-tools OBS Camera Plugin
+Copyright (C) 2026 CyberCoveLLC <jknapp85@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program. If not, see <https://www.gnu.org/licenses/>
+*/
+
+/* Adapted from obsproject/obs-plugintemplate (commit 3e7d7ac,
+ * 2025-12-09), the standard starting point for third-party OBS
+ * plugins. */
+
+#include "plugin-support.h"
+
+const char *PLUGIN_NAME = "@STPLUGIN_PROJECT_NAME@";
+const char *PLUGIN_VERSION = "@STPLUGIN_PROJECT_VERSION@";
+
+void obs_log(int log_level, const char *format, ...)
+{
+	size_t length = 4 + strlen(PLUGIN_NAME) + strlen(format);
+
+	char *template = malloc(length + 1);
+
+	snprintf(template, length, "[%s] %s", PLUGIN_NAME, format);
+
+	va_list(args);
+
+	va_start(args, format);
+	blogva(log_level, template, args);
+	va_end(args);
+
+	free(template);
+}

obs-adapter/src/plugin-support.h

@@ -0,0 +1,42 @@
+/*
+streamer-tools OBS Camera Plugin
+Copyright (C) 2026 CyberCoveLLC <jknapp85@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program. If not, see <https://www.gnu.org/licenses/>
+*/
+
+/* Adapted from obsproject/obs-plugintemplate (commit 3e7d7ac,
+ * 2025-12-09), the standard starting point for third-party OBS
+ * plugins. */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+
+extern const char *PLUGIN_NAME;
+extern const char *PLUGIN_VERSION;
+
+void obs_log(int log_level, const char *format, ...);
+extern void blogva(int log_level, const char *format, va_list args);
+
+#ifdef __cplusplus
+}
+#endif