Implements a custom `http.RoundTripper` that transparently retries 429 responses by reading the `RateLimit-Reset` header and respecting configurable max retries. The transport is composable with other transports (auth, debug) and can be dropped into any HTTP client to add intelligent rate-limit handling without altering business logic. Tests verify backoff timing, header parsing, and exhaustion behavior.

A generic validation framework built around a `Rule` interface (`Validate(string) error`) and reusable rule constructors (`Required`, `Slug`, `UUID`, `MinValue`). The `Validator` struct collects rules and runs them in sequence, returning a single aggregated error. The pattern is fully isolated and can be extracted into any Go project needing declarative input validation without framework dependency.

Defines a hierarchy of custom error types (`ValidationError`, `APIError`, `AuthError`, etc.) with exit codes, user-facing suggestions, and support for `errors.Is`/`errors.As`. The pattern provides structured error handling that preserves stack information while enabling downstream consumers (e.g., TUI or JSON output) to categorize and present errors appropriately. The wrapping and suggestion metadata are independent of any specific application domain.

A generic Go struct `Viewable[T]` that wraps any type `T` with a render function for text output while using the type's own JSON/YAML marshalling for structured formats. This separates presentation logic for human-readable output from machine-readable output, enabling consistent formatting across commands. The zero-dependency design (only uses standard library) makes it easily extractable into other CLI projects.

A portable credential store with automatic fallback from OS keychain (via `zalando/go-keyring`) to a tmpfs-backed file (`/dev/shm/`) with strict permissions (0700/0600), symlink rejection, and lock-file concurrency control. Handles token storage, retrieval, and deletion scoped by organization. The implementation is secure, platform-aware, and fully testable via a mock interface (`MockForTesting`), making it a model pattern for CLI tools requiring credential persistence.

Implements an `AggregateResolver` that chains multiple resolution strategies (from flag, from config, from git remote, interactive pick) with caching via `CachedPicker`. Each strategy is a separate implementation of the `Resolver` interface, allowing easy addition of new resolution methods. The pattern is generic enough to be reused for resolving any domain object (e.g., clusters, secrets) with similar multi-source lookup and user-choice fallback.