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.

skill/analyzer.py

@@ -165,17 +165,23 @@ class CLAUDEMDAnalyzer:
         issues = []
 
         # Check file length
-        if self.line_count > 400:
+        if self.line_count > 250:
             issues.append({
                 "type": "length_critical",
                 "severity": "high",
-                "message": f"File is too long ({self.line_count} lines). Recommended: split into modular files."
+                "message": f"File is too long ({self.line_count} lines). Hard cap is 150; split into modular files."
             })
-        elif self.line_count > 300:
+        elif self.line_count > 150:
+            issues.append({
+                "type": "length_warning",
+                "severity": "high",
+                "message": f"File exceeds the 150-line cap ({self.line_count} lines). Split now."
+            })
+        elif self.line_count > 120:
             issues.append({
                 "type": "length_warning",
                 "severity": "medium",
-                "message": f"File exceeds recommended 300 lines ({self.line_count} lines). Consider splitting."
+                "message": f"File is approaching the 150-line cap ({self.line_count} lines)."
             })
 
         # Check if file is too short
@@ -238,12 +244,13 @@ class CLAUDEMDAnalyzer:
         """
         score = 0
 
-        # Length appropriateness (25 points)
-        if 50 <= self.line_count <= 300:
+        # Length appropriateness (25 points). Hard cap is 150 lines; anything
+        # above that loses points sharply because it indicates context bloat.
+        if 50 <= self.line_count <= 150:
             score += 25
-        elif 30 <= self.line_count < 50 or 300 < self.line_count <= 400:
+        elif 30 <= self.line_count < 50 or 150 < self.line_count <= 200:
             score += 15
-        elif self.line_count > 400:
+        elif self.line_count > 200:
             score += 5
         else:
             score += 10
@@ -329,9 +336,9 @@ class CLAUDEMDAnalyzer:
                     recommendations.append(f"CRITICAL: {issue['message']}")
 
         # Length recommendations
-        if self.line_count > 300:
+        if self.line_count > 150:
             recommendations.append(
-                "Reduce root CLAUDE.md to <150 lines - move detailed guides to context-specific files"
+                "Reduce this CLAUDE.md to <=150 lines (hard cap) - move detail to context-specific files and chain them via @path imports"
             )
         elif self.line_count < 30:
             recommendations.append(