One way to record an error, and a name that reads as a query

dpm_module_info_of becomes dpm_get_module_info, joining the other two
readers on the context in stating that a call fetches a value.

Recording an error had two entry points doing the same write: the
exported dpm_set_last_error and an internal dpm_core::set_last_error
taking a std::string. The internal one is gone and the loader calls the
exported function, so a reason reaches the context by one path whether a
module or the library records it.

docs/PROSE/DESIGN.md

@@ -62,7 +62,7 @@ Releases the context: unloads every module handle it issued, closes log targets,
 `dpm_module* dpm_require(dpm_ctx* ctx, const char* name)`
 Resolves the module `name` in the module path and runs the full load-time validation sequence (see Load-Time Enforcement) if the module is not already loaded in this context. On success returns a module handle owned by the context (repeated calls return the same handle — modules are loaded at most once per context). On failure returns NULL and records the precise reason: not found, or validation step failed with the step and detail. No version criterion is applied here; compatibility is the caller's to determine from the reported version.
 
-`int dpm_module_info_of(dpm_ctx* ctx, dpm_module* mod, dpm_module_info* out)`
+`int dpm_get_module_info(dpm_ctx* ctx, dpm_module* mod, dpm_module_info* out)`
 Fills `out` with the loaded module's name, version, and description exactly as they were read at load (string pointers valid until context close). This is how a consumer obtains the version it will judge. The library attaches no meaning to the values. Returns 0 on success, nonzero if the module cannot be reported on.
 
 `int dpm_execute(dpm_ctx* ctx, dpm_module* mod, const char* command, int argc, char** argv)`