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-coding-style.md

@@ -1,32 +0,0 @@
----
-description: "Go coding style: gofmt mandatory, small interfaces, error wrapping with context"
-globs: ["**/*.go"]
-alwaysApply: false
----
-
-# Go Coding Style
-
-> This file extends [common/coding-style.md](../common/coding-style.md) with Go specific content.
-
-## Formatting
-
-- **gofmt** and **goimports** are mandatory — no style debates
-
-## Design Principles
-
-- Accept interfaces, return structs
-- Keep interfaces small (1-3 methods)
-
-## Error Handling
-
-Always wrap errors with context:
-
-```go
-if err != nil {
-    return fmt.Errorf("failed to create user: %w", err)
-}
-```
-
-## Reference
-
-See skill: `golang-patterns` for comprehensive Go idioms and patterns.