feat: add self-improving-agent plugin — auto-memory curation for Claude Code (#260)

New plugin: engineering-team/self-improving-agent/
- 5 skills: /si:review, /si:promote, /si:extract, /si:status, /si:remember
- 2 agents: memory-analyst, skill-extractor
- 1 hook: PostToolUse error capture (zero overhead on success)
- 3 reference docs: memory architecture, promotion rules, rules directory patterns
- 2 templates: rule template, skill template
- 20 files, 1,829 lines

Integrates natively with Claude Code's auto-memory (v2.1.32+).
Reads from ~/.claude/projects/<path>/memory/ — no duplicate storage.
Promotes proven patterns from MEMORY.md to CLAUDE.md or .claude/rules/.

Also:
- Added to marketplace.json (18 plugins total)
- Added to README (Skills Overview + install section)
- Updated badge count to 88+
- Regenerated .codex/skills-index.json + symlink

Co-authored-by: Leo <leo@openclaw.ai>

.codex/skills-index.json

@@ -3,7 +3,7 @@
   "name": "claude-code-skills",
   "description": "Production-ready skill packages for AI agents - Marketing, Engineering, Product, C-Level, PM, and RA/QM",
   "repository": "https://github.com/alirezarezvani/claude-skills",
-  "total_skills": 62,
+  "total_skills": 63,
   "skills": [
     {
       "name": "contract-and-proposal-writer",
@@ -77,6 +77,12 @@
       "category": "engineering",
       "description": "Production-grade Playwright testing toolkit. Generate tests, fix flaky failures, migrate from Cypress/Selenium, sync with TestRail, run on BrowserStack. 55 templates, 3 agents, smart reporting."
     },
+    {
+      "name": "self-improving-agent",
+      "source": "../../engineering-team/self-improving-agent",
+      "category": "engineering",
+      "description": "Curate Claude Code's auto-memory into durable project knowledge. Analyze MEMORY.md for patterns, promote proven learnings to CLAUDE.md and .claude/rules/, extract recurring solutions into reusable skills. Use when: (1) reviewing what Claude has learned about your project, (2) graduating a pattern from notes to enforced rules, (3) turning a debugging solution into a skill, (4) checking memory health and capacity."
+    },
     {
       "name": "senior-architect",
       "source": "../../engineering-team/senior-architect",
@@ -390,7 +396,7 @@
       "description": "Executive leadership and advisory skills"
     },
     "engineering": {
-      "count": 22,
+      "count": 23,
       "source": "../../engineering-team",
       "description": "Software engineering and technical skills"
     },

.codex/skills/self-improving-agent

@@ -0,0 +1 @@
+../../engineering-team/self-improving-agent