Module records and aliases

Installation records what a module reports about itself. dpm_install_module
opens a module once, writes its version and description to a .meta file in
/var/lib/dpm/metadata/, and records the alternate names it declared in
modules.aliases beside it. dpm_uninstall_module removes both, leaving the
module file in place.

dpm_list_modules reads those records and opens no module. A module with no
record lists with a version of <uninstalled> and still loads when a caller
names it. An unreadable or absent metadata directory costs the listing its
detail and costs nothing else.

Aliases give a module alternate names, declared through the new
dpm_module_aliases contract symbol or added with dpm_add_module_alias. A
name is recorded once: one already serving as an alias, or belonging to an
installed module, is refused rather than repointed. dpm_require matches a
name against the installed modules, then the alias table, then the module
path.

The metadata directory is a fifth override field and the -M flag, and
[modules] metadata in core.conf.

The test suite is four binaries covering context, modules, records, and
aliases, each a ctest case of its own, alongside the CLI cases.

tests/harness.hpp

@@ -0,0 +1,87 @@
+/**
+ * @file harness.hpp
+ * @brief What every test binary shares: counting, reporting, fixture paths
+ *
+ * Each test binary covers one area of the library and is registered as
+ * its own ctest case, so a failure names the area it happened in. This
+ * header carries what all of them need and nothing specific to any one.
+ *
+ * @copyright Copyright (c) 2026 SILO GROUP LLC
+ * @author Chris Punches <chris.punches@silogroup.org>
+ *
+ * Part of the Dark Horse Linux Package Manager (DPM)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+#pragma once
+
+#include <dpm/core.h>
+
+#include <cstdio>
+#include <cstring>
+
+#ifndef TEST_FIXTURE_MODULES
+#error "TEST_FIXTURE_MODULES must be defined"
+#endif
+#ifndef TEST_FIXTURE_CONF
+#error "TEST_FIXTURE_CONF must be defined"
+#endif
+#ifndef TEST_FIXTURE_METADATA
+#error "TEST_FIXTURE_METADATA must be defined"
+#endif
+#ifndef TEST_SCRATCH_ROOT
+#error "TEST_SCRATCH_ROOT must be defined"
+#endif
+
+/** Assertions run and assertions failed, reported by harness_report(). */
+static int g_checks   = 0;
+static int g_failures = 0;
+
+/**
+ * @brief Records one assertion and reports it when it fails
+ *
+ * Every failure names the file and line, so a ctest case that fails
+ * points at the assertion rather than at the binary.
+ */
+#define CHECK(cond)                                                        \
+    do {                                                                   \
+        g_checks++;                                                        \
+        if (!(cond)) {                                                     \
+            g_failures++;                                                  \
+            std::fprintf(stderr, "FAIL %s:%d: %s\n", __FILE__, __LINE__,   \
+                         #cond);                                           \
+        }                                                                  \
+    } while (0)
+
+/**
+ * @brief Reports whether the context's last error carries a substring
+ *
+ * @param ctx The context to read
+ * @param needle The text the reason is expected to contain
+ * @return true when a reason is recorded and contains needle
+ */
+static inline bool error_contains(dpm_ctx* ctx, const char* needle) {
+    const char* err = dpm_get_last_error(ctx);
+    return err != nullptr && std::strstr(err, needle) != nullptr;
+}
+
+/**
+ * @brief Prints the tally and yields the process exit status
+ *
+ * @return 0 when every assertion passed, 1 otherwise
+ */
+static inline int harness_report(const char* suite) {
+    std::printf("%s: %d checks, %d failures\n", suite, g_checks, g_failures);
+    return g_failures == 0 ? 0 : 1;
+}