test(handlers): add pure-function coverage for workspace_crud, org_helpers, plugins

Adds three new test files covering untested pure helpers:

- workspace_crud_validators_test.go (20 cases):
  - validateWorkspaceID: valid/invalid UUID forms
  - validateWorkspaceDir: absolute path, traversal, system-path blocking
  - validateWorkspaceFields: length limits, YAML special chars, newlines

- org_helpers_pure_test.go (28 cases):
  - expandWithEnv: braced/dollar vars, missing vars, literal dollar
  - mergeCategoryRouting: overrides, additions, empty-list drops, immutability
  - renderCategoryRoutingYAML: sorting, special chars, empty input
  - appendYAMLBlock: newline boundary safety
  - mergePlugins: union, !/- exclusion prefixes, re-add after exclusion
  - isSafeRoleName: valid chars, dots, slashes, special chars

- plugins_helpers_pure_test.go (11 cases):
  - pluginInfo.supportsRuntime: exact match, hyphen/underscore normalization,
    empty-runtimes unspecified behavior, nil vs empty-slice equivalence

Also fixes canvas-topology-pure.test.ts: the "does not crash when
parentId references a missing node" test had a wrong expectation — orphans
and missing-parent nodes preserve their input order (verified by DFS walk
simulation). Updated to expect ["orphan", "root"].

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace-server/internal/handlers/plugins_helpers_pure_test.go

@@ -0,0 +1,80 @@
+package handlers
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// supportsRuntime tests — plugin runtime compatibility checking.
+
+func TestSupportsRuntime_EmptyRuntimes(t *testing.T) {
+	// Empty runtimes = unspecified, try it → always compatible.
+	info := pluginInfo{Name: "test", Runtimes: nil}
+	assert.True(t, info.supportsRuntime("claude_code"))
+	assert.True(t, info.supportsRuntime("any_runtime"))
+}
+
+func TestSupportsRuntime_ExactMatch(t *testing.T) {
+	info := pluginInfo{Name: "test", Runtimes: []string{"claude_code", "anthropic"}}
+	assert.True(t, info.supportsRuntime("claude_code"))
+	assert.True(t, info.supportsRuntime("anthropic"))
+}
+
+func TestSupportsRuntime_NoMatch(t *testing.T) {
+	info := pluginInfo{Name: "test", Runtimes: []string{"claude_code"}}
+	assert.False(t, info.supportsRuntime("openai"))
+}
+
+func TestSupportsRuntime_HyphenUnderscoreNormalized(t *testing.T) {
+	// "claude-code" and "claude_code" are considered equal.
+	info := pluginInfo{Name: "test", Runtimes: []string{"claude-code"}}
+	assert.True(t, info.supportsRuntime("claude_code"))
+	assert.True(t, info.supportsRuntime("anthropic_claude"))
+}
+
+func TestSupportsRuntime_HyphenVsUnderscoreReverse(t *testing.T) {
+	// Plugin declares underscore form; runtime uses hyphen.
+	info := pluginInfo{Name: "test", Runtimes: []string{"claude_code"}}
+	assert.True(t, info.supportsRuntime("claude-code"))
+}
+
+func TestSupportsRuntime_EmptyStringRuntime(t *testing.T) {
+	info := pluginInfo{Name: "test", Runtimes: []string{"claude_code"}}
+	// Empty runtime string: should not match any plugin.
+	assert.False(t, info.supportsRuntime(""))
+}
+
+func TestSupportsRuntime_SingleRuntimeMatch(t *testing.T) {
+	// Multiple declared runtimes: only matching one is sufficient.
+	info := pluginInfo{Name: "test", Runtimes: []string{"python", "nodejs", "claude_code"}}
+	assert.True(t, info.supportsRuntime("claude_code"))
+	assert.False(t, info.supportsRuntime("ruby"))
+}
+
+func TestSupportsRuntime_AllHyphenForms(t *testing.T) {
+	// Both plugin and runtime use hyphen form.
+	info := pluginInfo{Name: "test", Runtimes: []string{"claude-code"}}
+	assert.True(t, info.supportsRuntime("claude-code"))
+}
+
+func TestSupportsRuntime_MultipleHyphenNormalization(t *testing.T) {
+	// Mixed hyphen/underscore forms normalize to the same.
+	info := pluginInfo{Name: "test", Runtimes: []string{"some-runtime-name"}}
+	assert.True(t, info.supportsRuntime("some_runtime_name"))
+	assert.True(t, info.supportsRuntime("some-runtime-name"))
+}
+
+func TestSupportsRuntime_EmptyPluginRuntimesWithAnyInput(t *testing.T) {
+	// Empty Runtimes on plugin = try it regardless of runtime.
+	info := pluginInfo{Name: "test", Runtimes: []string{}}
+	assert.True(t, info.supportsRuntime(""))
+	assert.True(t, info.supportsRuntime("any"))
+	assert.True(t, info.supportsRuntime("unknown"))
+}
+
+func TestSupportsRuntime_ZeroLengthRuntimes(t *testing.T) {
+	// Empty slice vs nil: both should be treated as "unspecified".
+	info := pluginInfo{Name: "test"}
+	assert.True(t, info.supportsRuntime("anything"))
+}