Fix paste ownership, input bounds, and IPC validation

Supersedes #5745, #5746, and #5747.

src/main/linear/issue-context-errors.test.ts

@@ -0,0 +1,27 @@
+import { describe, expect, it, vi } from 'vitest'
+import { sanitizeLinearErrorMessage } from './issue-context-errors'
+
+describe('sanitizeLinearErrorMessage', () => {
+  it('removes stack frames without regex line splitting', () => {
+    const splitSpy = vi.spyOn(String.prototype, 'split')
+    try {
+      expect(
+        sanitizeLinearErrorMessage('Linear request failed\r\n    at request (sdk.js:10:2)')
+      ).toBe('Linear request failed')
+      const usedStackSplit = splitSpy.mock.calls.some(
+        ([separator]) => separator instanceof RegExp && separator.source === '\\r?\\n\\s+at\\s+'
+      )
+      expect(usedStackSplit).toBe(false)
+    } finally {
+      splitSpy.mockRestore()
+    }
+  })
+
+  it('redacts sensitive Linear payloads after trimming stack frames', () => {
+    expect(
+      sanitizeLinearErrorMessage(
+        'Request failed authorization: Bearer secret-token\n    at request (sdk.js:10:2)'
+      )
+    ).toBe('Request failed authorization: Bearer [REDACTED]')
+  })
+})