feat(v0.5.1): Linux portability baseline

- justfile: add build-linux, build-windows, build-all (output to dist/)
- .gitignore: cover ctask, ctask-*, dist/
- scripts/install.sh + scripts/uninstall.sh: POSIX equivalents of .ps1
- remove WorkspacePath metadata field (no production readers; legacy
  task.yaml files continue to parse silently)

Linux smoke-test on WSL/container pending.
See audit-report.md and v0.5.1-spec.md.

internal/workspace/create.go

@@ -135,7 +135,6 @@ func Create(opts CreateOpts) (*CreateResult, error) {
 		Type:          taskType,
 		Mode:          opts.Mode,
 		Agent:         opts.Agent,
-		WorkspacePath: wsDir,
 		ArchivedAt:    nil,
 	}
 	if opts.IsProject {

internal/workspace/metadata.go

@@ -26,7 +26,6 @@ type TaskMeta struct {
 	Type          string     `yaml:"type"`
 	Mode          string     `yaml:"mode"`
 	Agent         string     `yaml:"agent"`
-	WorkspacePath string     `yaml:"workspace_path"`
 	ArchivedAt    *time.Time `yaml:"archived_at"`
 	LaunchDir     string     `yaml:"launch_dir,omitempty"`
 }

internal/workspace/metadata_test.go

@@ -18,7 +18,6 @@ func TestWriteMetaLockedHappyPath(t *testing.T) {
 		CreatedAt: now, UpdatedAt: now,
 		Status: "active", Category: "general", Type: "task",
 		Mode: "local", Agent: "claude",
-		WorkspacePath: dir,
 	}
 
 	if err := WriteMetaLocked(metaPath, meta); err != nil {
@@ -78,7 +77,6 @@ func TestWriteAndReadMeta(t *testing.T) {
 		Category:      "general",
 		Mode:          "local",
 		Agent:         "claude",
-		WorkspacePath: "/home/warren/ai-workspaces/general/20260405_arch-notes",
 		ArchivedAt:    nil,
 	}
 
@@ -123,7 +121,6 @@ func TestMetaYAMLFieldsPresent(t *testing.T) {
 		Category:      "general",
 		Mode:          "local",
 		Agent:         "claude",
-		WorkspacePath: "/tmp/test",
 	}
 
 	WriteMeta(path, meta)
@@ -131,7 +128,7 @@ func TestMetaYAMLFieldsPresent(t *testing.T) {
 	data, _ := os.ReadFile(path)
 	content := string(data)
 
-	for _, field := range []string{"id:", "slug:", "title:", "created_at:", "updated_at:", "status:", "category:", "type:", "mode:", "agent:", "workspace_path:", "archived_at:"} {
+	for _, field := range []string{"id:", "slug:", "title:", "created_at:", "updated_at:", "status:", "category:", "type:", "mode:", "agent:", "archived_at:"} {
 		if !strings.Contains(content, field) {
 			t.Errorf("missing field %s in YAML output", field)
 		}
@@ -154,7 +151,6 @@ func TestMetaTypeRoundTrip(t *testing.T) {
 		Type:          "project",
 		Mode:          "local",
 		Agent:         "claude",
-		WorkspacePath: "/tmp/billing",
 	}
 	if err := WriteMeta(path, meta); err != nil {
 		t.Fatalf("WriteMeta: %v", err)
@@ -234,7 +230,6 @@ func TestMetaArchive(t *testing.T) {
 		Category:      "general",
 		Mode:          "local",
 		Agent:         "claude",
-		WorkspacePath: "/tmp/test",
 	}
 
 	WriteMeta(path, meta)

internal/workspace/query_test.go

@@ -40,7 +40,6 @@ func createTestWorkspaceFull(t *testing.T, root, category, dirName, status, task
 		Type:          taskType,
 		Mode:          "local",
 		Agent:         "claude",
-		WorkspacePath: dir,
 	}
 	WriteMeta(filepath.Join(dir, "task.yaml"), meta)
 }
@@ -186,7 +185,6 @@ func createFlatProjectWorkspaceFull(t *testing.T, root, dirName string, updatedA
 		Type:          "project",
 		Mode:          "local",
 		Agent:         "claude",
-		WorkspacePath: dir,
 	}
 	WriteMeta(filepath.Join(dir, "task.yaml"), meta)
 }