Add override config layer for forced retry behavior

[kamui]

Summary

Adds Retriable.override and Retriable.reset_override APIs that force retry settings over local call options.

Retriable.override(tries: 1, base_interval: 0)

Precedence

override > local options > configure defaults

Use case

Test short-circuiting: in test environments, tries: 1 must win even when production code passes explicit local options like Retriable.retriable(tries: 5). Overrides also force retry behavior over inherited custom intervals unless intervals is explicitly overridden.

API

• Retriable.override(opts) accepts a non-empty hash of config keys to force globally.
• Retriable.reset_override clears the override.
• Contexts are supported: Retriable.override(contexts: { api: { tries: 1 } }).
• Invalid top-level keys and invalid context override keys raise ArgumentError, consistent with Retriable.retriable.

Example: Rails test setup

# config/initializers/retriable.rb
Retriable.configure do |c|
  c.tries = 3
  c.base_interval = 0.5
end

if Rails.env.test?
  Retriable.override(tries: 1, base_interval: 0, rand_factor: 0)
end

Implementation

The override is stored as a sparse hash delta and merged lazily at each retriable/with_context call. Hash-valued options replace lower-precedence values rather than deep-merging, so forced options remain authoritative.

Changes

• lib/retriable.rb — adds override, reset_override, validation, and supporting merge helpers
• spec/retriable_spec.rb — tests override precedence, contexts, edge cases, validation, and order isolation
• README.md — new Override section, updated Testing section with override examples
• CHANGELOG.md / lib/retriable/version.rb — version and changelog entries

Closes #108.