fix: transitive path deps resolve relative to parent dep's root

Path dependencies of transitive deps were resolved relative to the
main project root, which fails for workspace members when greeter
depends on core via path = "../core" but the build target is apps/hello.

Fix: add resolveRoot to WorkItem so child deps resolve relative to
their parent dep's directory. Also fix CI to pick the newest built
mcpp binary (avoids stale cached binaries from different fingerprints).

Author: Sunrisepeak

src/cli.cppm

@@ -1210,6 +1210,7 @@ prepare_build(bool print_fingerprint,
         std::string                          requestedBy;         // who asked for it
         std::string                          originalConstraint;  // spec.version BEFORE pinning (for SemVer merge)
         std::size_t                          consumerDepIndex;    // dep_manifests slot of who pushed this child; kMainConsumer for main
+        std::filesystem::path                resolveRoot;         // base dir for relative path deps (empty = use project root)
     };
     std::deque<WorkItem> worklist;
 
@@ -1454,12 +1455,12 @@ prepare_build(bool print_fingerprint,
     // caller wants them; they're never propagated transitively.
     const std::string mainPkgLabel = m->package.name;
     for (auto& [n, s] : m->dependencies) {
-        worklist.push_back({n, s, mainPkgLabel, s.version, kMainConsumer});
+        worklist.push_back({n, s, mainPkgLabel, s.version, kMainConsumer, {}});
     }
     if (includeDevDeps) {
         for (auto& [n, s] : m->devDependencies) {
             worklist.push_back({n, s, mainPkgLabel + " (dev-dep)",
-                                s.version, kMainConsumer});
+                                s.version, kMainConsumer, {}});
         }
     }
 
@@ -1708,7 +1709,7 @@ prepare_build(bool print_fingerprint,
                         dep_manifests[it->second.depIndex]->dependencies) {
                     worklist.push_back({child_name, child_spec, newLabel,
                                         child_spec.version,
-                                        it->second.depIndex});
+                                        it->second.depIndex, {}});
                 }
                 continue;
             }
@@ -1720,9 +1721,12 @@ prepare_build(bool print_fingerprint,
         std::filesystem::path dep_root;
 
         if (spec.isPath()) {
-            // Path-based: resolve relative to project root.
+            // Path-based: resolve relative to the consumer's root dir.
+            // For top-level deps this is the project root; for transitive
+            // deps it's the parent dep's directory (stored in resolveRoot).
             dep_root = spec.path;
-            if (dep_root.is_relative()) dep_root = *root / dep_root;
+            auto base = item.resolveRoot.empty() ? *root : item.resolveRoot;
+            if (dep_root.is_relative()) dep_root = base / dep_root;
             dep_root = std::filesystem::weakly_canonical(dep_root);
         } else if (spec.isGit()) {
             // Git-based (M4 #5): clone into ~/.mcpp/git/<hash>/<rev>/
@@ -1857,7 +1861,7 @@ prepare_build(bool print_fingerprint,
         const std::size_t selfIdx = dep_manifests.size() - 1;
         for (auto& [child_name, child_spec] : dep_manifests.back()->dependencies) {
             worklist.push_back({child_name, child_spec, thisDepLabel,
-                                child_spec.version, selfIdx});
+                                child_spec.version, selfIdx, dep_root});
         }
     }