docs: document bd setup command

Add comprehensive documentation for the bd setup command which was
largely undocumented (GH#518):

- CLI_REFERENCE.md: Add new "Editor Integration" section documenting
  bd setup claude/cursor/aider commands with all flags
- INSTALLING.md: Fix incorrect reference to "bd hooks install" for
  editor integration - should be "bd setup <editor>"
- CLAUDE_INTEGRATION.md: Add Installation section with bd setup claude
  examples

Fixes: GH#518

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/CLAUDE_INTEGRATION.md

@@ -81,6 +81,29 @@ They should be:
 
 Users who want custom Skills can create their own, but beads doesn't ship with or require them.
 
+## Installation
+
+```bash
+# Install Claude Code hooks globally
+bd setup claude
+
+# Install for this project only
+bd setup claude --project
+
+# Use stealth mode (flush only, no git operations)
+bd setup claude --stealth
+
+# Check installation status
+bd setup claude --check
+
+# Remove hooks
+bd setup claude --remove
+```
+
+**What it installs:**
+- SessionStart hook: Runs `bd prime` when Claude Code starts a session
+- PreCompact hook: Runs `bd prime` before context compaction to preserve workflow instructions
+
 ## Related Files
 
 - `cmd/bd/prime.go` - Context generation