refactor(ipc): harden channels and unify IPC contracts

tests/unit/file-ipc-paths.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, it } from 'vitest'
+import path from 'path'
+import { isPathWithinAllowedRoots } from '../../src/main/ipc/file-handler'
+
+describe('File IPC Path Guard', () => {
+  it('accepts path under allowed root', () => {
+    const root = path.resolve('C:/safe/root')
+    const file = path.join(root, 'nested', 'file.txt')
+    expect(isPathWithinAllowedRoots(file, [root])).toBe(true)
+  })
+
+  it('rejects path outside allowed roots', () => {
+    const root = path.resolve('C:/safe/root')
+    const outside = path.resolve('C:/other/location/file.txt')
+    expect(isPathWithinAllowedRoots(outside, [root])).toBe(false)
+  })
+})

tests/unit/ipc-index.test.ts

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+import { describe, it, expect } from 'vitest'
+import { withErrorHandling } from '../../src/main/ipc'
+import { ValidationError } from '../../src/main/types/errors'
+
+describe('IPC Result Wrapper', () => {
+  it('wraps successful values into IpcResult.data', async () => {
+    const result = await withErrorHandling(async () => ({ value: 42 }), 'test:success')
+    expect(result.success).toBe(true)
+    expect(result.data).toEqual({ value: 42 })
+  })
+
+  it('wraps exceptions into IpcResult.error/code', async () => {
+    const result = await withErrorHandling(async () => {
+      throw new ValidationError('Invalid input', 'VAL_INVALID_INPUT')
+    }, 'test:failure')
+
+    expect(result.success).toBe(false)
+    expect(result.error).toBe('Invalid input')
+    expect(result.code).toBe('VAL_INVALID_INPUT')
+  })
+})

tests/unit/preload-surface.test.ts

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+import { describe, expect, it } from 'vitest'
+import fs from 'fs'
+import path from 'path'
+
+describe('Preload API Surface', () => {
+  it('does not expose ipcRenderer in window typings', () => {
+    const dtsPath = path.resolve(process.cwd(), 'src/preload/index.d.ts')
+    const content = fs.readFileSync(dtsPath, 'utf-8')
+    expect(content.includes('ipcRenderer:')).toBe(false)
+  })
+})