Add stable hashed identity for speed dial actions

tests/slic3rutils/CMakeLists.txt

@@ -5,6 +5,7 @@ add_executable(${_TEST_NAME}_tests
     test_plugin_capability_identifier.cpp
     test_plugin_install.cpp
     test_plugin_sort.cpp
+    test_speed_dial_action_id.cpp
     )
 
 if (MSVC)

tests/slic3rutils/test_speed_dial_action_id.cpp

@@ -0,0 +1,28 @@
+#include <catch2/catch_all.hpp>
+
+#include <slic3r/GUI/SpeedDialActionId.hpp>
+
+using Slic3r::GUI::speed_dial_action_id;
+
+TEST_CASE("speed_dial_action_id is deterministic and opaque", "[speeddial][id]") {
+    const std::string a = speed_dial_action_id("pack.py", "Do Thing");
+    const std::string b = speed_dial_action_id("pack.py", "Do Thing");
+    CHECK(a == b);                 // stable within a run
+    CHECK(a.size() == 16);         // 64-bit -> 16 hex chars
+    CHECK(a.find_first_not_of("0123456789abcdef") == std::string::npos);
+}
+
+TEST_CASE("speed_dial_action_id separates key and capability", "[speeddial][id]") {
+    // The 0x1f separator prevents (key+cap) run-together collisions:
+    // ("ab","c") must not equal ("a","bc").
+    CHECK(speed_dial_action_id("ab", "c") != speed_dial_action_id("a", "bc"));
+    CHECK(speed_dial_action_id("k", "one") != speed_dial_action_id("k", "two"));
+    CHECK(speed_dial_action_id("k1", "cap") != speed_dial_action_id("k2", "cap"));
+}
+
+TEST_CASE("speed_dial_action_id golden vector locks cross-run stability", "[speeddial][id]") {
+    // why: this value is PERSISTED as a config key; if the algorithm ever drifts,
+    // every saved favourite/stat silently orphans. Pin a known input->output.
+    // FNV-1a 64-bit of bytes: 'k','e','y',0x1f,'c','a','p'
+    CHECK(speed_dial_action_id("key", "cap") == "c54ad154fb2c9187");
+}