feat(plugin): ship as Claude Code plugin with 150-line cap and sync command

Turns ClaudeForge into an installable Claude Code plugin and adds the
missing pieces for a clean lifecycle: hard line-cap enforcement, modular
chaining via @path imports, a sync/cleanup command, and Explore-agent
delegation for project discovery.

- .claude-plugin/plugin.json: plugin manifest registering both skills,
  both commands, and the guardian agent (installable via /plugin marketplace
  add alirezarezvani/ClaudeForge && /plugin install claudeforge)
- skill/validator.py: MAX_RECOMMENDED_LINES 300 -> 150 (warning at 120)
- skill/template_selector.py: target_lines capped at 150 across all
  team sizes (solo 75 / small 100 / medium 125 / large 150) so any
  single CLAUDE.md fits within the cap; bigger projects spread content
  across modular sub-files
- skill/analyzer.py: length thresholds, quality scoring, and recommendations
  rebased on the 150 cap (was 300/400)
- skill/generator.py: modular root now emits @path imports next to the
  human-readable links; every sub-CLAUDE.md gets a back-link header
  pointing to ../CLAUDE.md (markdown + @import) for bidirectional chaining
- command/sync-claude-md.md: new /sync-claude-md command that inventories
  every CLAUDE.md, prunes stale references, enforces the 150 cap by
  splitting into sub-files, and repairs the root <-> sub chain
- command/enhance-claude-md.md: discovery phase now delegates the deep
  codebase scan to the Explore subagent to keep context lean
- install.sh / install.ps1: each command in command/ installs as its own
  ~/.claude/commands/<name>.md (legacy bundle backed up on upgrade)
- skill/SKILL.md, CLAUDE.md, README.md, CHANGELOG.md: docs updated for
  the plugin install path, sync command, and new line cap

Verified via smoke test: validator constants, template targets, generator
output line counts across 5 presets (all <= 150), context files with
backlinks, @-import chain in modular root, idempotent merge_with_existing,
validator status transitions at the new cap, analyzer quality differential,
and plugin manifest JSON shape with all referenced paths existing on disk.

install.sh

@@ -159,7 +159,8 @@ echo ""
 print_info "Installation will create:"
 echo "  • Skill:    $SKILLS_DIR/claudeforge-skill/"
 echo "  • Skill:    $SKILLS_DIR/karpathy-guidelines/"
-echo "  • Command:  $COMMANDS_DIR/enhance-claude-md/"
+echo "  • Command:  $COMMANDS_DIR/enhance-claude-md.md"
+echo "  • Command:  $COMMANDS_DIR/sync-claude-md.md"
 echo "  • Agent:    $AGENTS_DIR/claude-md-guardian.md"
 echo ""
 
@@ -203,15 +204,32 @@ cp -r skill/karpathy-guidelines "$SKILLS_DIR/karpathy-guidelines"
 rm -rf "$SKILLS_DIR/claudeforge-skill/karpathy-guidelines"
 print_success "Karpathy guidelines installed → $SKILLS_DIR/karpathy-guidelines/"
 
-# Install slash command
-print_info "Installing /enhance-claude-md command..."
+# Install slash commands. Each .md file in command/ is installed as its own
+# top-level command file so it registers as /<name> rather than as a nested
+# /<dir>:<name>. README.md and other non-command files are skipped.
+print_info "Installing slash commands..."
+
+# Migrate legacy bundle directory if present.
 if [ -d "$COMMANDS_DIR/enhance-claude-md" ]; then
-    print_warning "Existing command found. Creating backup..."
+    print_warning "Legacy command bundle found. Creating backup..."
     mv "$COMMANDS_DIR/enhance-claude-md" "$COMMANDS_DIR/enhance-claude-md.backup.$(date +%Y%m%d_%H%M%S)"
     print_success "Backup created"
 fi
-cp -r command "$COMMANDS_DIR/enhance-claude-md"
-print_success "Command installed → $COMMANDS_DIR/enhance-claude-md/"
+
+for cmd_file in command/*.md; do
+    cmd_basename=$(basename "$cmd_file")
+    # Skip the directory's own README.
+    if [ "$cmd_basename" = "README.md" ]; then
+        continue
+    fi
+    cmd_target="$COMMANDS_DIR/$cmd_basename"
+    if [ -f "$cmd_target" ]; then
+        print_warning "Existing $cmd_basename found. Creating backup..."
+        mv "$cmd_target" "$cmd_target.backup.$(date +%Y%m%d_%H%M%S)"
+    fi
+    cp "$cmd_file" "$cmd_target"
+    print_success "Command installed → $cmd_target"
+done
 
 # Install guardian agent
 print_info "Installing claude-md-guardian agent..."
@@ -319,12 +337,14 @@ echo ""
 if [ "$SCOPE" == "user-level" ]; then
     echo "  rm -rf ~/.claude/skills/claudeforge-skill"
     echo "  rm -rf ~/.claude/skills/karpathy-guidelines"
-    echo "  rm -rf ~/.claude/commands/enhance-claude-md"
+    echo "  rm -f  ~/.claude/commands/enhance-claude-md.md"
+    echo "  rm -f  ~/.claude/commands/sync-claude-md.md"
     echo "  rm -f ~/.claude/agents/claude-md-guardian.md"
 else
     echo "  rm -rf ./.claude/skills/claudeforge-skill"
     echo "  rm -rf ./.claude/skills/karpathy-guidelines"
-    echo "  rm -rf ./.claude/commands/enhance-claude-md"
+    echo "  rm -f  ./.claude/commands/enhance-claude-md.md"
+    echo "  rm -f  ./.claude/commands/sync-claude-md.md"
     echo "  rm -f ./.claude/agents/claude-md-guardian.md"
 fi
 echo ""