fix(shared-manager): normalize plugin registry paths to canonical ~/.claude/

Replaces instance-specific paths (/.ccs/instances/<name>/) with
canonical /.claude/ paths in installed_plugins.json after linking.

Fixes #276

tests/unit/shared-manager.test.ts

@@ -0,0 +1,104 @@
+/**
+ * Unit tests for SharedManager - plugin registry path normalization
+ */
+import { describe, it, expect, beforeEach, afterEach } from 'bun:test';
+import * as fs from 'fs';
+import * as path from 'path';
+import * as os from 'os';
+
+// Test the normalization regex pattern directly
+const normalizePluginPaths = (content: string): string => {
+  return content.replace(/\/\.ccs\/instances\/[^/]+\//g, '/.claude/');
+};
+
+describe('SharedManager', () => {
+  describe('normalizePluginRegistryPaths', () => {
+    describe('regex pattern', () => {
+      it('should replace instance paths with canonical claude path', () => {
+        const input = '/home/user/.ccs/instances/ck/plugins/cache/plugin/0.0.2';
+        const expected = '/home/user/.claude/plugins/cache/plugin/0.0.2';
+        expect(normalizePluginPaths(input)).toBe(expected);
+      });
+
+      it('should handle different instance names', () => {
+        const inputs = [
+          '/home/user/.ccs/instances/work/plugins/cache/plugin/1.0.0',
+          '/home/user/.ccs/instances/personal/plugins/cache/plugin/1.0.0',
+          '/home/user/.ccs/instances/test-account/plugins/cache/plugin/1.0.0',
+        ];
+        for (const input of inputs) {
+          expect(normalizePluginPaths(input)).toContain('/.claude/');
+          expect(normalizePluginPaths(input)).not.toContain('/.ccs/instances/');
+        }
+      });
+
+      it('should handle multiple occurrences', () => {
+        const input = JSON.stringify({
+          plugins: {
+            'plugin-a': [{ installPath: '/home/user/.ccs/instances/ck/plugins/a' }],
+            'plugin-b': [{ installPath: '/home/user/.ccs/instances/work/plugins/b' }],
+          },
+        });
+        const result = normalizePluginPaths(input);
+        expect(result).not.toContain('/.ccs/instances/');
+        expect(result.match(/\.claude/g)?.length).toBe(2);
+      });
+
+      it('should not modify already-canonical paths', () => {
+        const input = '/home/user/.claude/plugins/cache/plugin/0.0.2';
+        expect(normalizePluginPaths(input)).toBe(input);
+      });
+
+      it('should be idempotent', () => {
+        const input = '/home/user/.ccs/instances/ck/plugins/cache/plugin/0.0.2';
+        const first = normalizePluginPaths(input);
+        const second = normalizePluginPaths(first);
+        expect(first).toBe(second);
+      });
+
+      it('should preserve JSON structure', () => {
+        const original = {
+          version: 2,
+          plugins: {
+            'claude-hud@claude-hud': [
+              {
+                scope: 'user',
+                installPath: '/home/kai/.ccs/instances/ck/plugins/cache/claude-hud/claude-hud/0.0.2',
+                version: '0.0.2',
+              },
+            ],
+          },
+        };
+        const input = JSON.stringify(original, null, 2);
+        const result = normalizePluginPaths(input);
+
+        // Should be valid JSON
+        expect(() => JSON.parse(result)).not.toThrow();
+
+        // Should have normalized path
+        const parsed = JSON.parse(result);
+        expect(parsed.plugins['claude-hud@claude-hud'][0].installPath).toBe(
+          '/home/kai/.claude/plugins/cache/claude-hud/claude-hud/0.0.2'
+        );
+      });
+    });
+
+    describe('edge cases', () => {
+      it('should handle empty object', () => {
+        const input = JSON.stringify({});
+        expect(normalizePluginPaths(input)).toBe(input);
+      });
+
+      it('should handle plugins without installPath', () => {
+        const input = JSON.stringify({ plugins: {} });
+        expect(normalizePluginPaths(input)).toBe(input);
+      });
+
+      it('should handle Windows-style paths (backslash)', () => {
+        // Windows paths use backslashes, regex should not match
+        const input = 'C:\\Users\\user\\.ccs\\instances\\ck\\plugins\\cache';
+        expect(normalizePluginPaths(input)).toBe(input);
+      });
+    });
+  });
+});