chore: add CLAUDE.md

Author: MacroPower

.github/instructions/go.instructions.md

@@ -0,0 +1,97 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+`kat` is a rule-based rendering engine and terminal UI for Kubernetes manifests. It automatically invokes manifest generators (Helm, Kustomize, etc.) and provides a navigable view of rendered resources with live reloading, validation, and an optional MCP server.
+
+## Build & Development Commands
+
+```bash
+# Format code
+task format
+
+# Lint all (Go, YAML, Actions, Renovate, GoReleaser)
+task lint
+
+# Run tests
+task test
+
+# Run a single test
+go test ./pkg/config -run TestConfigLoader
+```
+
+## Architecture
+
+### Entry Point & CLI
+
+- `cmd/kat/main.go` - Entry point using charmbracelet/fang
+- `internal/cli/` - CLI commands, flags, and environment binding
+
+### Core Packages (`pkg/`)
+
+**Rendering Pipeline:**
+
+- `pkg/command/` - Command execution orchestration, file watching, event broadcasting
+- `pkg/profile/` - Profile definitions with CEL-based source/reload expressions, hooks, plugins
+- `pkg/rule/` - CEL-based rule matching for automatic profile selection
+- `pkg/expr/` - CEL expression compilation and evaluation with custom functions (pathBase, pathExt, yamlPath, etc.)
+
+**Kubernetes & YAML:**
+
+- `pkg/kube/` - Kubernetes resource parsing and object representation
+- `pkg/yaml/` - YAML encoding/decoding, validation, error formatting
+
+**UI (Bubble Tea):**
+
+- `pkg/ui/` - Main TUI program and state management
+- `pkg/ui/list/` - Resource list with fuzzy filtering
+- `pkg/ui/pager/` - YAML document viewer with syntax highlighting
+- `pkg/ui/menu/` - Configuration menu for profile/path changes
+- `pkg/ui/overlay/` - Error/loading overlays
+- `pkg/ui/theme/` - Chroma-based theming
+
+**Other:**
+
+- `pkg/config/` - Configuration loading, validation, and default config embedding
+- `pkg/mcp/` - Model Context Protocol server for AI integrations
+- `pkg/execs/` - Command execution utilities
+- `pkg/keys/` - Keybinding definitions
+
+### Data Flow
+
+1. CLI parses args and loads config from `$XDG_CONFIG_HOME/kat/config.yaml`
+2. `command.Runner` matches path against rules to select a profile
+3. Profile executes command with hooks (init, preRender, postRender)
+4. Rendered YAML is parsed into `kube.Resource` objects
+5. Events broadcast to UI and MCP server subscribers
+6. UI displays resources in list/pager views
+
+## Code Style
+
+### Go Conventions
+
+- Document all exported items with doc comments
+- Use `[Name]` syntax for Go doc links
+- Package documentation in `doc.go` files
+- Wrap errors with `fmt.Errorf("context: %w", err)` - no "failed" or "error" in messages
+- Use global error variables for common errors
+
+### Testing
+
+- Use `github.com/stretchr/testify/assert` and `require`
+- Table-driven tests with `map[string]struct{}` format
+- Field names: `input`, `want`, `got`, `err`
+- Always use `t.Parallel()` in all tests
+- Create test packages (`package foo_test`) testing public API
+- Use `require.ErrorIs` for error type checking
+
+## Key Dependencies
+
+- `github.com/charmbracelet/bubbletea` - TUI framework
+- `github.com/google/cel-go` - CEL expression engine
+- `github.com/alecthomas/chroma/v2` - Syntax highlighting
+- `github.com/goccy/go-yaml` - YAML with anchors/aliases support
+- `github.com/fsnotify/fsnotify` - File watching
+- `github.com/modelcontextprotocol/go-sdk` - MCP server