Feature request: allow cooldown via CLI flag (--cooldown-days)

[mkusaka]

Feature request: allow cooldown via CLI flag (--cooldown-days)

Summary

Allow the cooldown (minimum release age) to be set directly via a CLI flag.

Motivation

• For one-off or CI runs, it's useful to say "don't pin tags newer than N days" without depending on a Dependabot config or a user config file.
• Per-repo overrides are better left to config files — repeating key=value flags per action doesn't scale — so the flag should set only the global CooldownConfig.DefaultDays.

Proposal

Add --cooldown-days N (int). When set, it takes precedence over .github/dependabot.yml and ~/.config/gh-actions-lock/config.yml and applies to CooldownConfig.DefaultDays. Treat --cooldown-days 0 as disabling cooldown for that run (making a separate --no-cooldown unnecessary).

Precedence: flag > dependabot.yml > user config > none