fix(index): index list and the router read the same effective indices on a workspace root

`mcpp index list` lists what resolution searches: a member's own [indices],
[workspace.indices], and a root's own table by position. effective_indices
recognises a workspace root by its own [workspace] table (e2e 44).

Author: Sunrisepeak

src/pm/index_management.cppm

@@ -16,6 +16,7 @@ import mcpp.lockfile;
 import mcpp.manifest;
 import mcpp.platform;
 import mcpp.project;
+import mcpp.pm.index_route;
 import mcpp.ui;
 import mcpp.xlings;
 
@@ -95,15 +96,15 @@ export int index_list() {
     // Show project-level custom indices from mcpp.toml [indices].
     auto root = mcpp::project::find_manifest_root(std::filesystem::current_path());
     if (root) {
-        // The effective manifest: a member inherits the workspace's
-        // `[indices]` (#690, W4).
-        std::optional<mcpp::manifest::Manifest> m;
-        if (auto effective = mcpp::project::load_effective_manifest(*root))
-            m = std::move(effective->manifest);
-        if (m && !m->indices.empty()) {
+        // The effective `[indices]`: a member's own, `[workspace.indices]`, and
+        // a workspace root's own read by position (#690; SPEC-004 §9.12, §9.13).
+        // One function with the index router, so the list names what
+        // resolution searches.
+        const auto indices = mcpp::pm::effective_indices(*root);
+        if (!indices.empty()) {
             std::println("");
             std::println("Project indices (mcpp.toml):");
-            for (auto& [name, spec] : m->indices) {
+            for (auto& [name, spec] : indices) {
                 if (spec.is_local()) {
                     std::println("  {:<15}  {}  (local path)", name, spec.path.string());
                 } else {

src/pm/index_route.cppm

@@ -256,11 +256,11 @@ IndexMap effective_indices(const std::filesystem::path& root) {
     // by name; the root's own [indices] by position when it has none of the
     // former), whose relative `path` is anchored at the ROOT (#224).
     auto wsRoot = mcpp::project::find_workspace_root(root);
-    if (wsRoot.empty()) return m->indices;
     // The workspace root itself: its own [indices], and what it gives every
     // member, its root package included.
     std::error_code ec;
-    if (std::filesystem::equivalent(wsRoot, root, ec)) {
+    if (m->workspace.present || (!wsRoot.empty() && std::filesystem::equivalent(wsRoot, root, ec))) {
+        if (m->workspace.present) wsRoot = root;
         if (m->layer)
             for (auto const& [name, idx] : m->layer->indices) {
                 auto [it, inserted] = m->indices.try_emplace(name, idx);
@@ -269,6 +269,7 @@ IndexMap effective_indices(const std::filesystem::path& root) {
             }
         return m->indices;
     }
+    if (wsRoot.empty()) return m->indices;
     auto ws = mcpp::manifest::load(wsRoot / "mcpp.toml");
     if (!ws || !ws->workspace.present) return m->indices;
     mcpp::project::inherit_workspace_indices(*m, *ws, wsRoot);