fix(manifest): partitions -> separate modules + umbrella (GCC 15 cross link)

GCC 15 (the aarch64-linux-musl cross toolchain) drops implicit template
instantiations of module-attached types from partition object files —
undefined refs to std::map<..., ScanOverride>::map() etc. at final link.
Same split, same importer API, but as three plain modules re-exported by
an umbrella mcpp.manifest, the pattern the rest of the codebase already
links with everywhere. Shared parser helpers become exported (separate-
module visibility requires it).

Author: Sunrisepeak

src/manifest/manifest.cppm

@@ -1,13 +1,18 @@
 // mcpp.manifest — manifest data model + the two descriptor formats.
 //
-// Split into partitions for architectural clarity (one data model, two
-// independent surface grammars):
-//   :types  shared data model (Manifest, Target, BuildConfig, errors)
-//   :toml   mcpp.toml parsing (projects / packages on disk)
-//   :xpkg   xpkg .lua `mcpp = {}` segment parsing (index descriptors)
+// Umbrella module: one data model, two independent surface grammars.
+// Split as SEPARATE modules (not partitions): GCC 15's partition handling
+// drops implicit template instantiations of module-attached types
+// (std::map<..., ScanOverride> etc.) from partition objects, breaking the
+// aarch64 cross link; plain modules re-exported here behave identically
+// for importers and link everywhere.
+//
+//   mcpp.manifest.types  shared data model (Manifest, Target, errors)
+//   mcpp.manifest.toml   mcpp.toml parsing (projects / packages on disk)
+//   mcpp.manifest.xpkg   xpkg .lua `mcpp = {}` segment (index descriptors)
 
 export module mcpp.manifest;
 
-export import :types;
-export import :toml;
-export import :xpkg;
+export import mcpp.manifest.types;
+export import mcpp.manifest.toml;
+export import mcpp.manifest.xpkg;

src/manifest/toml.cppm

@@ -1,8 +1,8 @@
 // mcpp.manifest:toml — load and validate mcpp.toml.
 
-export module mcpp.manifest:toml;
+export module mcpp.manifest.toml;
 
-import :types;
+import mcpp.manifest.types;
 import std;
 import mcpp.libs.toml;
 import mcpp.pm.dep_spec;

src/manifest/types.cppm

@@ -3,7 +3,7 @@
 // Everything both descriptor formats (mcpp.toml, xpkg .lua) synthesize
 // into, plus format-agnostic helpers. No parsing lives here.
 
-export module mcpp.manifest:types;
+export module mcpp.manifest.types;
 
 import std;
 import mcpp.pm.dep_spec;     // M5.x pm/ subsystem refactor: DependencySpec lives here
@@ -401,8 +401,9 @@ bool has_lib_target(const Manifest& manifest);
 
 } // namespace mcpp::manifest
 
-// ── module-linkage helpers shared by the :toml and :xpkg parsers ──
-namespace mcpp::manifest {
+// ── helpers shared by the toml and xpkg parsers (exported: separate
+//    modules need them reachable; they live in the manifest namespace) ──
+export namespace mcpp::manifest {
 
 bool starts_with_std_flag(std::string_view flag) {
     return flag == "-std" || flag.starts_with("-std=");

src/manifest/xpkg.cppm

@@ -1,9 +1,9 @@
 // mcpp.manifest:xpkg — parse the `mcpp = {}` segment of xpkg .lua
 // descriptors (tiny Lua-subset reader; we never execute Lua).
 
-export module mcpp.manifest:xpkg;
+export module mcpp.manifest.xpkg;
 
-import :types;
+import mcpp.manifest.types;
 import std;
 import mcpp.pm.dep_spec;
 import mcpp.pm.dependency_selector;