feat(linkedin): add auto-clipboard on all content commands

Adds Bash to allowed-tools and clipboard-helper.mjs auto-copy to:
post.md, quick.md, react.md, pipeline.md, first-post.md,
video.md, multiplatform.md, carousel.md.

Each command auto-copies the final post/caption text to clipboard
after presenting the draft. Replaces manual copy-paste instructions
in first-post.md (=== COPY FROM HERE ===) with auto-copy.

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

plugins/linkedin-thought-leadership/commands/video.md

@@ -10,6 +10,7 @@ allowed-tools:
   - Glob
   - Grep
   - Write
+  - Bash
   - AskUserQuestion
 ---
 
@@ -142,7 +143,7 @@ Angle:    [from 8 thought leadership angles]
 
 [Line-by-line caption text with timing]
 
-━━━ POST CAPTION ━━━━━━━━━━━━━━━━━━━━━━━━━
+━━━ POST CAPTION (copied to clipboard) ━━━
 
 [200-400 char text to accompany the video]
 
@@ -159,6 +160,12 @@ Style: [minimal / branded / text-heavy]
 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 ```
 
+Auto-copy the POST CAPTION text to clipboard silently:
+```bash
+printf '%s' '<POST_CAPTION_TEXT>' | node ${CLAUDE_PLUGIN_ROOT}/hooks/scripts/clipboard-helper.mjs
+```
+Then confirm: "Post caption copied to clipboard."
+
 ## Step 7: Refinement Cycle
 
 Use AskUserQuestion: