feat(linkedin): add clipboard-helper.mjs — cross-platform clipboard utility

TDD: 13 tests written first, then implementation.
Exports copyToClipboard(text) and clipboardAvailable() — never throws.
Supports darwin (pbcopy), win32 (clip), linux (xclip/xsel fallback).
Dual standalone/import mode following personalization-score.mjs pattern.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/linkedin-thought-leadership/hooks/scripts/__tests__/clipboard-helper.test.mjs

@@ -0,0 +1,86 @@
+import { describe, test } from 'node:test';
+import assert from 'node:assert/strict';
+import { clipboardAvailable, copyToClipboard } from '../clipboard-helper.mjs';
+
+describe('clipboardAvailable', () => {
+  test('returns object with available and platform fields', () => {
+    const result = clipboardAvailable();
+    assert.equal(typeof result.available, 'boolean');
+    assert.equal(typeof result.platform, 'string');
+  });
+
+  test('returns available: true on macOS (darwin)', () => {
+    if (process.platform !== 'darwin') return;
+    const result = clipboardAvailable();
+    assert.equal(result.available, true);
+    assert.equal(result.platform, 'darwin');
+  });
+
+  test('returns a recognized platform string', () => {
+    const result = clipboardAvailable();
+    assert.ok(
+      ['darwin', 'win32', 'linux'].includes(result.platform),
+      `Unexpected platform: ${result.platform}`
+    );
+  });
+});
+
+describe('copyToClipboard', () => {
+  test('returns object with success and platform fields', () => {
+    const result = copyToClipboard('test clipboard text');
+    assert.equal(typeof result.success, 'boolean');
+    assert.equal(typeof result.platform, 'string');
+  });
+
+  test('copies text successfully on macOS', () => {
+    if (process.platform !== 'darwin') return;
+    const result = copyToClipboard('clipboard-helper test 2026');
+    assert.equal(result.success, true);
+    assert.equal(result.platform, 'darwin');
+  });
+
+  test('handles empty string input gracefully', () => {
+    const result = copyToClipboard('');
+    assert.equal(result.success, true);
+    assert.equal(typeof result.platform, 'string');
+  });
+
+  test('handles multiline text', () => {
+    const multiline = 'Line 1\nLine 2\nLine 3';
+    const result = copyToClipboard(multiline);
+    assert.equal(result.success, true);
+  });
+
+  test('handles special characters (quotes, ampersands, backticks)', () => {
+    const special = 'He said "hello" & she said \'goodbye\' `code` $VAR';
+    const result = copyToClipboard(special);
+    assert.equal(result.success, true);
+  });
+
+  test('handles unicode/emoji text', () => {
+    const unicode = '🚀 Thought leadership → impact';
+    const result = copyToClipboard(unicode);
+    assert.equal(result.success, true);
+  });
+
+  test('never throws — always returns a result object', () => {
+    assert.doesNotThrow(() => copyToClipboard(null));
+    assert.doesNotThrow(() => copyToClipboard(undefined));
+    assert.doesNotThrow(() => copyToClipboard(123));
+  });
+
+  test('returns success: false for non-string input', () => {
+    const result = copyToClipboard(null);
+    assert.equal(result.success, false);
+  });
+});
+
+describe('module exports', () => {
+  test('exports clipboardAvailable as a function', () => {
+    assert.equal(typeof clipboardAvailable, 'function');
+  });
+
+  test('exports copyToClipboard as a function', () => {
+    assert.equal(typeof copyToClipboard, 'function');
+  });
+});

plugins/linkedin-thought-leadership/hooks/scripts/clipboard-helper.mjs

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+#!/usr/bin/env node
+// Cross-platform clipboard helper for linkedin-thought-leadership plugin
+// Copies text to system clipboard using platform-native commands.
+// Standalone: reads stdin and copies it. Import: export { copyToClipboard, clipboardAvailable }
+
+import { execSync } from 'node:child_process';
+import { dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const PLATFORM_COMMANDS = {
+  darwin: { copy: 'pbcopy', check: 'which pbcopy' },
+  win32: { copy: 'clip', check: 'where clip' },
+  linux: { copy: 'xclip -selection clipboard', check: 'which xclip' },
+};
+
+const LINUX_FALLBACK = { copy: 'xsel --clipboard --input', check: 'which xsel' };
+
+/**
+ * Check if clipboard is available on this platform.
+ * @returns {{ available: boolean, platform: string }}
+ */
+export function clipboardAvailable() {
+  const platform = process.platform;
+  const commands = PLATFORM_COMMANDS[platform];
+
+  if (!commands) {
+    return { available: false, platform };
+  }
+
+  try {
+    execSync(commands.check, { stdio: 'ignore' });
+    return { available: true, platform };
+  } catch {
+    // Linux fallback: try xsel if xclip not found
+    if (platform === 'linux') {
+      try {
+        execSync(LINUX_FALLBACK.check, { stdio: 'ignore' });
+        return { available: true, platform };
+      } catch {
+        return { available: false, platform };
+      }
+    }
+    return { available: false, platform };
+  }
+}
+
+/**
+ * Copy text to the system clipboard.
+ * Never throws — always returns a result object.
+ * @param {string} text - The text to copy
+ * @returns {{ success: boolean, platform: string }}
+ */
+export function copyToClipboard(text) {
+  const platform = process.platform;
+
+  if (typeof text !== 'string') {
+    return { success: false, platform };
+  }
+
+  const commands = PLATFORM_COMMANDS[platform];
+  if (!commands) {
+    return { success: false, platform };
+  }
+
+  // Determine which copy command to use
+  let copyCmd = commands.copy;
+  if (platform === 'linux') {
+    try {
+      execSync(commands.check, { stdio: 'ignore' });
+    } catch {
+      try {
+        execSync(LINUX_FALLBACK.check, { stdio: 'ignore' });
+        copyCmd = LINUX_FALLBACK.copy;
+      } catch {
+        return { success: false, platform };
+      }
+    }
+  }
+
+  try {
+    execSync(copyCmd, { input: text, stdio: ['pipe', 'ignore', 'ignore'] });
+    return { success: true, platform };
+  } catch {
+    return { success: false, platform };
+  }
+}
+
+// Standalone execution: read stdin and copy
+if (process.argv[1] === fileURLToPath(import.meta.url)) {
+  let input = '';
+  process.stdin.setEncoding('utf-8');
+  process.stdin.on('data', (chunk) => { input += chunk; });
+  process.stdin.on('end', () => {
+    const result = copyToClipboard(input);
+    if (result.success) {
+      process.stdout.write('COPIED\n');
+    } else {
+      process.stdout.write(`FAILED:${result.platform}\n`);
+      process.exitCode = 1;
+    }
+  });
+}