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/golang-patterns.md

@@ -1,45 +0,0 @@
----
-description: "Go patterns: functional options, small interfaces, dependency injection"
-globs: ["**/*.go"]
-alwaysApply: false
----
-
-# Go Patterns
-
-> This file extends [common/patterns.md](../common/patterns.md) with Go specific content.
-
-## Functional Options
-
-```go
-type Option func(*Server)
-
-func WithPort(port int) Option {
-    return func(s *Server) { s.port = port }
-}
-
-func NewServer(opts ...Option) *Server {
-    s := &Server{port: 8080}
-    for _, opt := range opts {
-        opt(s)
-    }
-    return s
-}
-```
-
-## Small Interfaces
-
-Define interfaces where they are used, not where they are implemented.
-
-## Dependency Injection
-
-Use constructor functions to inject dependencies:
-
-```go
-func NewUserService(repo UserRepository, logger Logger) *UserService {
-    return &UserService{repo: repo, logger: logger}
-}
-```
-
-## Reference
-
-See skill: `golang-patterns` for comprehensive Go patterns including concurrency, error handling, and package organization.