address review: remove .cursor/ duplicate, use is not None checks

Changes based on CodeRabbit review feedback:

1. Remove entire .cursor/ directory — it was an identical copy of the
   main skills/commands/agents/rules, causing maintenance drift.
   Users of Cursor can reference the canonical files directly.

2. Use explicit `is not None` checks instead of truthiness for
   parsed['input'] and parsed['output']. Empty strings or empty
   dicts are valid values that should be preserved.

.cursor/rules/common-security.md

@@ -1,34 +0,0 @@
----
-description: "Mandatory security checks, secret management, and security response protocol"
-alwaysApply: true
----
-
-# Security Guidelines
-
-## Mandatory Security Checks
-
-Before ANY commit:
-- [ ] No hardcoded secrets (API keys, passwords, tokens)
-- [ ] All user inputs validated
-- [ ] SQL injection prevention (parameterized queries)
-- [ ] XSS prevention (sanitized HTML)
-- [ ] CSRF protection enabled
-- [ ] Authentication/authorization verified
-- [ ] Rate limiting on all endpoints
-- [ ] Error messages don't leak sensitive data
-
-## Secret Management
-
-- NEVER hardcode secrets in source code
-- ALWAYS use environment variables or a secret manager
-- Validate that required secrets are present at startup
-- Rotate any secrets that may have been exposed
-
-## Security Response Protocol
-
-If security issue found:
-1. STOP immediately
-2. Use **security-reviewer** agent
-3. Fix CRITICAL issues before continuing
-4. Rotate any exposed secrets
-5. Review entire codebase for similar issues