fix(richdem): correct package lookup and validate serial terrain core

Author: Sunrisepeak

.agents/docs/2026-10-13-add-richdem-plan.md

@@ -0,0 +1,21 @@
+# Add compat.richdem
+
+The pinned revision 9a1c97bb2529e386451a7dd54768b8b74bb4d620 declares
+project version 2.2.11 in upstream CMakeLists.txt. It is not a release tag;
+the descriptor preserves the PR's requested source snapshot and version.
+The archive hash was checked twice. License: MIT.
+
+This Form B build compiles richdem.cpp, random.cpp and terrain generation
+sources, exposing upstream include/. It is deliberately the serial core:
+GDAL, Boost serialization and OpenMP are disabled. The proposed gdal feature
+was removed because adding gdal.cpp alone leaves USEGDAL disabled and cannot
+supply the required SDK and runtime. No unsupported feature is advertised.
+
+The descriptor lives under pkgs/c/compat.richdem.lua, matching the full
+package name; the consumer redirects compat to this checkout. It fills a
+3x3 depression and verifies random-state save/restore, exercising both the
+public terrain algorithm and linked core symbols.
+
+No mirror upload was performed; plain-string GLOBAL URLs provide CN fallback.
+Local validation with the CI-pinned mcpp 2026.10.1.2 and gcc 16.1.0:
+`mcpp test -p richdem`: `test result ok. 1 passed; 0 failed`.

README.md

@@ -63,6 +63,8 @@ the online index; open a PR and confirm CI is green.
 A PR runs lint and tests only the workspace members that depend on the changed descriptors; after the merge,
 `deploy-site` publishes the site.
 
+Additional example: [`compat.richdem`](pkgs/c/compat.richdem.lua) — C++ sources, serial terrain analysis; [`consumer test`](tests/examples/richdem/mcpp.toml).
+
 ## Documentation
 
 - [Library shapes and descriptor templates](docs/package-types.md)

README.zh-CN.md

@@ -59,6 +59,8 @@ agent(如 Claude Code)即可:
 
 提交 PR 后,CI 执行 lint,并只测试依赖了被修改描述符的 workspace 成员;合并后,`deploy-site` 发布站点。
 
+新增示例: [`compat.richdem`](pkgs/c/compat.richdem.lua) — C++ sources, serial terrain analysis; [`消费测试`](tests/examples/richdem/mcpp.toml)。
+
 ## 文档
 
 - [库形态与描述符模板](docs/zh/package-types.md)

pkgs/r/compat.richdem.lua pkgs/c/compat.richdem.luapkgs/r/compat.richdem.lua renamed to pkgs/c/compat.richdem.lua

@@ -1,11 +1,9 @@
 -- Form B inline descriptor for RichDEM, a C++ library for high-performance
 -- terrain analysis.
 --
--- RichDEM's public headers are under include/richdem and its standalone
--- library sources are under src/. GDAL support is optional upstream: enabling
--- the feature matches CMake's USE_GDAL option by defining USEGDAL and adding
--- the GDAL implementation source. Consumers enabling that feature must also
--- provide GDAL headers and the GDAL library in their environment.
+-- Serial core build: GDAL, Boost serialization and OpenMP are disabled.
+-- GDAL needs a define, headers and a runtime dependency, so a sources-only
+-- feature cannot enable it correctly. Do not advertise an inert gdal feature.
 package = {
     spec        = "1",
     namespace   = "compat",
@@ -48,12 +46,6 @@ package = {
             "*/src/terrain_generation/PerlinNoise.cpp",
         },
         targets      = { ["richdem"] = { kind = "lib" } },
-        features     = {
-            ["gdal"] = {
-                defines = { "USEGDAL" },
-                sources = { "*/src/gdal.cpp" },
-            },
-        },
         deps = {},
     },
 }

tests/examples/richdem/mcpp.toml

@@ -4,3 +4,6 @@ version = "0.1.0"
 
 [dependencies.compat]
 richdem = "2.2.11"
+
+[indices]
+compat = { path = "../../.." }

tests/examples/richdem/tests/core.cpp

@@ -1,8 +1,17 @@
-#include <richdem/common/constants.hpp>
+#include <richdem/common/Array2D.hpp>
 #include <richdem/common/random.hpp>
+#include <richdem/depressions/depressions.hpp>
 
 int main() {
+    richdem::Array2D<double> dem(3, 3, 5.0);
+    dem(1, 1) = 1.0;
+    richdem::FillDepressions<richdem::Topology::D8>(dem);
+    if (dem(1, 1) != 5.0 || dem(0, 0) != 5.0) return 1;
+
     richdem::seed_rand(1);
-    const auto value = richdem::uniform_rand_int(1, 10);
-    return value >= 1 && value <= 10 ? 0 : 1;
+    const auto state = richdem::SaveRandomState();
+    const int first = richdem::uniform_rand_int(1, 10);
+    richdem::SetRandomState(state);
+    return first >= 1 && first <= 10 &&
+           richdem::uniform_rand_int(1, 10) == first ? 0 : 2;
 }