feat: collision hard errors + rename resolution

- flat per-type deployed namespace enforced across own items and all sources
- own-vs-vendored and vendored-vs-vendored collisions abort with both parties named
- --rename upstream=deployed resolves collisions; on-disk folder always equals
  deployed name; rename targets are validated against new collisions
- checks run before any tree mutation; validate re-checks the namespace offline

internal/e2e/collide_test.go

@@ -0,0 +1,121 @@
+package e2e
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/m3tam3re/agent-lib/internal/lockfile"
+)
+
+func ownSkillFixture(h *harness, t *testing.T) {
+	t.Helper()
+	dir := filepath.Join(h.workDir, "skills", "good-skill")
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	os.WriteFile(filepath.Join(dir, "SKILL.md"), []byte("---\nname: Own Good\n---\n"), 0o644)
+}
+
+func TestCollisionOwnVsVendored(t *testing.T) {
+	h := newHarness(t)
+	ownSkillFixture(h, t)
+	standardFixture(h, t)
+
+	out, err := h.run(t, "vendor", "add", "superpowers", h.upstreamDir)
+	if err == nil {
+		t.Fatalf("own-vs-vendored collision must fail:\n%s", out)
+	}
+	for _, want := range []string{"collides", "own", "good-skill"} {
+		if !contains(out, want) {
+			t.Errorf("error must contain %q:\n%s", want, out)
+		}
+	}
+	if _, err := os.Stat(filepath.Join(h.workDir, "external")); err == nil {
+		t.Error("collision must abort before any tree mutation")
+	}
+	if _, err := os.Stat(filepath.Join(h.workDir, lockfile.FileName)); err == nil {
+		t.Error("collision must not write a lockfile")
+	}
+}
+
+func TestCollisionVendoredVsVendored(t *testing.T) {
+	h := newHarness(t)
+	standardFixture(h, t)
+	h.mustRun(t, "vendor", "add", "first", h.upstreamDir)
+
+	out, err := h.run(t, "vendor", "add", "second", h.upstreamDir)
+	if err == nil {
+		t.Fatalf("vendored-vs-vendored collision must fail:\n%s", out)
+	}
+	for _, want := range []string{"collides", "first"} {
+		if !contains(out, want) {
+			t.Errorf("error must name both parties (%q missing):\n%s", want, out)
+		}
+	}
+}
+
+func TestCollisionResolvedByRename(t *testing.T) {
+	h := newHarness(t)
+	ownSkillFixture(h, t)
+	standardFixture(h, t)
+
+	out := h.mustRun(t, "vendor", "add", "superpowers", h.upstreamDir,
+		"--rename", "good-skill=superpowers-good-skill")
+	if !contains(out, "renamed") && !contains(out, "materialized") {
+		t.Errorf("rename resolution should report success:\n%s", out)
+	}
+
+	renamed := filepath.Join(h.workDir, "external/superpowers/skills/superpowers-good-skill/SKILL.md")
+	if _, err := os.Stat(renamed); err != nil {
+		t.Fatal("renamed folder must carry the deployed name")
+	}
+	original := filepath.Join(h.workDir, "external/superpowers/skills/good-skill")
+	if _, err := os.Stat(original); err == nil {
+		t.Error("upstream folder name must not appear after rename")
+	}
+
+	lock := readFile(t, filepath.Join(h.workDir, lockfile.FileName))
+	if !contains(lock, `"good-skill": "superpowers-good-skill"`) {
+		t.Errorf("rename map must be pinned in the lockfile:\n%s", lock)
+	}
+
+	if out := h.mustRun(t, "validate"); !contains(out, "valid") {
+		t.Errorf("renamed state must validate:\n%s", out)
+	}
+}
+
+func TestCollisionRenameToAnotherCollision(t *testing.T) {
+	h := newHarness(t)
+	ownSkillFixture(h, t)
+	standardFixture(h, t)
+
+	out, err := h.run(t, "vendor", "add", "superpowers", h.upstreamDir,
+		"--rename", "good-skill=broken-skill")
+	if err == nil {
+		t.Fatalf("renaming onto an existing deployed name must fail:\n%s", out)
+	}
+	if !contains(out, "collides") {
+		t.Errorf("error must report the collision:\n%s", out)
+	}
+}
+
+func TestValidateDetectsHandEditedCollision(t *testing.T) {
+	h := newHarness(t)
+	standardFixture(h, t)
+	h.mustRun(t, "vendor", "add", "superpowers", h.upstreamDir)
+	h.mustRun(t, "vendor", "add", "second-source", h.upstreamDir, "--include", "good-skill",
+		"--rename", "good-skill=second-good")
+
+	mutateLockfile(t, h, func(lf *lockfile.Lockfile) {
+		lf.Sources["second-source"].Renames["good-skill"] = "broken-skill"
+	})
+
+	out, err := h.run(t, "validate")
+	if err == nil {
+		t.Fatalf("hand-edited rename collision must fail validation:\n%s", out)
+	}
+	if !contains(out, "collision") {
+		t.Errorf("rule must be reported as collision:\n%s", out)
+	}
+}