feat(pluginhost): refactor and enhance plugin system with new execution and thinking capabilities

- Removed `examples/plugin/main.go` and `internal/pluginhost/loader_plugin.go` after migrating to a more modular system.
- Introduced `streamBridge` in `internal/pluginhost/stream_bridge.go` for efficient stream handling and communication.
- Added examples of `thinking` plugins written in both Rust and Go under `examples/plugin/thinking`.
- Enhanced test coverage for plugin host system changes, including stream chunk translation and thinking logic.
- Improved API compatibility and ensured backward-compatible upgrades for plugin execution.

examples/plugin/cli/c/src/plugin.c

@@ -0,0 +1,117 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#if defined(_WIN32)
+#define CLIPROXY_EXPORT __declspec(dllexport)
+#else
+#define CLIPROXY_EXPORT __attribute__((visibility("default")))
+#endif
+
+#define ABI_VERSION 1
+
+typedef struct {
+	void* ptr;
+	size_t len;
+} cliproxy_buffer;
+
+typedef int (*cliproxy_host_call_fn)(void*, const char*, const uint8_t*, size_t, cliproxy_buffer*);
+typedef void (*cliproxy_host_free_fn)(void*, size_t);
+
+typedef struct {
+	uint32_t abi_version;
+	void* host_ctx;
+	cliproxy_host_call_fn call;
+	cliproxy_host_free_fn free_buffer;
+} cliproxy_host_api;
+
+typedef int (*cliproxy_plugin_call_fn)(const char*, const uint8_t*, size_t, cliproxy_buffer*);
+typedef void (*cliproxy_plugin_free_fn)(void*, size_t);
+typedef void (*cliproxy_plugin_shutdown_fn)(void);
+
+typedef struct {
+	uint32_t abi_version;
+	cliproxy_plugin_call_fn call;
+	cliproxy_plugin_free_fn free_buffer;
+	cliproxy_plugin_shutdown_fn shutdown;
+} cliproxy_plugin_api;
+
+static const cliproxy_host_api* stored_host = NULL;
+
+static void write_response(cliproxy_buffer* response, const char* text) {
+	if (response == NULL || text == NULL) {
+		return;
+	}
+	size_t len = strlen(text);
+	void* ptr = malloc(len);
+	if (ptr == NULL) {
+		response->ptr = NULL;
+		response->len = 0;
+		return;
+	}
+	memcpy(ptr, text, len);
+	response->ptr = ptr;
+	response->len = len;
+}
+
+static void call_host(const char* method, const char* payload) {
+	if (stored_host == NULL || stored_host->call == NULL || method == NULL) {
+		return;
+	}
+	cliproxy_buffer response = {0};
+	const uint8_t* request = (const uint8_t*)payload;
+	size_t request_len = payload == NULL ? 0 : strlen(payload);
+	if (stored_host->call(stored_host->host_ctx, method, request, request_len, &response) == 0 && response.ptr != NULL && stored_host->free_buffer != NULL) {
+		stored_host->free_buffer(response.ptr, response.len);
+	}
+}
+
+static int plugin_call(const char* method, const uint8_t* request, size_t request_len, cliproxy_buffer* response) {
+	if (response != NULL) {
+		response->ptr = NULL;
+		response->len = 0;
+	}
+	if (method == NULL) {
+		write_response(response, "{\"ok\":false,\"error\":{\"code\":\"invalid_method\",\"message\":\"method is required\"}}");
+		return 1;
+	}
+	if (strcmp(method, "plugin.register") == 0) {
+		write_response(response, "{\"ok\":true,\"result\":{\"schema_version\":1,\"metadata\":{\"Name\":\"example-cli-c\",\"Version\":\"0.1.0\",\"Author\":\"router-for-me\",\"GitHubRepository\":\"https://github.com/router-for-me/CLIProxyAPI\",\"Logo\":\"https://example.invalid/example-cli-c.png\",\"ConfigFields\":[]},\"capabilities\":{\"command_line_plugin\":true}}}");
+		return 0;
+	}
+	if (strcmp(method, "plugin.reconfigure") == 0) {
+		write_response(response, "{\"ok\":true,\"result\":{\"schema_version\":1,\"metadata\":{\"Name\":\"example-cli-c\",\"Version\":\"0.1.0\",\"Author\":\"router-for-me\",\"GitHubRepository\":\"https://github.com/router-for-me/CLIProxyAPI\",\"Logo\":\"https://example.invalid/example-cli-c.png\",\"ConfigFields\":[]},\"capabilities\":{\"command_line_plugin\":true}}}");
+		return 0;
+	}
+	if (strcmp(method, "command_line.register") == 0) {
+		write_response(response, "{\"ok\":true,\"result\":{\"Flags\":[{\"Name\":\"example-cli-c-command\",\"Usage\":\"Run the example plugin command\",\"Type\":\"bool\"}]}}");
+		return 0;
+	}
+	if (strcmp(method, "command_line.execute") == 0) {
+		write_response(response, "{\"ok\":true,\"result\":{\"Stdout\":\"ImV4YW1wbGUtY2xpLWMgY29tbWFuZCBleGVjdXRlZFxcbiI=\",\"ExitCode\":0}}");
+		return 0;
+	}
+	write_response(response, "{\"ok\":false,\"error\":{\"code\":\"unknown_method\",\"message\":\"unknown method\"}}");
+	(void)request;
+	(void)request_len;
+	return 0;
+}
+
+static void plugin_free(void* ptr, size_t len) {
+	(void)len;
+	free(ptr);
+}
+
+static void plugin_shutdown(void) {}
+
+CLIPROXY_EXPORT int cliproxy_plugin_init(const cliproxy_host_api* host, cliproxy_plugin_api* plugin) {
+	if (plugin == NULL) {
+		return 1;
+	}
+	stored_host = host;
+	plugin->abi_version = ABI_VERSION;
+	plugin->call = plugin_call;
+	plugin->free_buffer = plugin_free;
+	plugin->shutdown = plugin_shutdown;
+	return 0;
+}