chore: Add agentic coding tooling

.crosslink/rules/go.md

@@ -0,0 +1,44 @@
+### Go Best Practices
+
+#### Code Style
+- Use `gofmt` for formatting
+- Use `golint` and `go vet` for linting
+- Follow effective Go guidelines
+- Keep functions short and focused
+
+#### Error Handling
+```go
+// GOOD: Check and handle errors
+func readConfig(path string) (*Config, error) {
+    data, err := os.ReadFile(path)
+    if err != nil {
+        return nil, fmt.Errorf("reading config: %w", err)
+    }
+
+    var config Config
+    if err := json.Unmarshal(data, &config); err != nil {
+        return nil, fmt.Errorf("parsing config: %w", err)
+    }
+    return &config, nil
+}
+
+// BAD: Ignoring errors
+func readConfig(path string) *Config {
+    data, _ := os.ReadFile(path)  // Don't ignore errors
+    var config Config
+    json.Unmarshal(data, &config)
+    return &config
+}
+```
+
+#### Concurrency
+- Use channels for communication between goroutines
+- Use `sync.WaitGroup` for waiting on multiple goroutines
+- Use `context.Context` for cancellation and timeouts
+- Avoid shared mutable state; prefer message passing
+
+#### Security
+- Use `html/template` for HTML output (auto-escaping)
+- Use parameterized queries for SQL
+- Validate all input at API boundaries
+- Use `crypto/rand` for secure random numbers