Wave 5+6: plugin ABI hardening, build modernization, ABI/security docs

Wave 5 (9 parallel agents):
- W1.1 atomic diag callback + DLL handle release on shutdown (lin)
- W2.1 unify cross-DLL heap discipline (host->alloc/free/strdup) (chen)
- W2.2 secure_zero api_key on shutdown for deepseek/anthropic (cao)
- W3 CMake modernization: target-based cxx_std_20, dstalk_boost_config
  INTERFACE lib, root-level RUNTIME_OUTPUT_DIRECTORY (hu)
- W4 GitHub Actions CI with dynamic Linux/Windows matrix (ma)
- W5.1 SSE buffer_body to cut peak memory ~67% on 32K streams (zhou)
- W6.1 LSP JSON-RPC frame parser hardened against header reordering (sun)
- W7 smoke test: copy plugin DLLs post-build + Boost.JSON src.hpp fix
  for full 9-plugin load coverage (wang)
- W8.1 README slimmed 398->92, Diataxis docs/ skeleton (deng)

Wave 6 (6 parallel agents):
- W9.1 docs/explanation: architecture + plugin-lifecycle (deng)
- W9.3 log credential leak audit (0 vulns, audit trail in
  docs/explanation/security-logging.md) (cao)
- W9.4 docs/reference/plugin-abi.md - 7-point ABI contract (lin)
- W9.6 CLI /history command + status integration (zhao)
- W9.8 plugin_loader fault tolerance: per-plugin failure no longer
  aborts dstalk_init (huang)
- W9.10 host_api unit tests: tests/host_api_test.cpp, 8 cases (liu)

CEO oversight (preexisting bugs fixed during Wave 5 verification):
- lsp_plugin.cpp:449 forward decl mismatch (int vs void)
- tools_plugin.cpp:109 missing forward decl

Multi-agent collaboration framework:
- agents/WORKFLOW.md: 6-stage protocol, two-tier governance,
  prompt template, technical constraints registry

Build: cmake --build 0 error / 0 warning. Tests: 2/2 100% pass.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

plugins/file-io/CMakeLists.txt

@@ -1,9 +1,5 @@
 add_library(plugin-file-io SHARED src/file_io_plugin.cpp)
 
-target_include_directories(plugin-file-io PRIVATE
-    ${CMAKE_SOURCE_DIR}/dstalk-core/include
-)
-
 target_link_libraries(plugin-file-io PRIVATE dstalk)
 
 set_target_properties(plugin-file-io PROPERTIES

plugins/file-io/src/file_io_plugin.cpp

@@ -29,8 +29,8 @@ static int file_read(const char* path, char** content) {
         return -1;
     }
 
-    // Allocate buffer (+1 for null terminator)
-    char* buf = (char*)malloc((size_t)fsize + 1);
+    // Allocate buffer via host allocator (+1 for null terminator)
+    char* buf = (char*)g_host->alloc((size_t)fsize + 1);
     if (!buf) {
         fclose(fp);
         return -1;
@@ -40,7 +40,7 @@ static int file_read(const char* path, char** content) {
     fclose(fp);
 
     if (read_bytes != (size_t)fsize) {
-        free(buf);
+        g_host->free(buf);
         return -1;
     }