v0.3.0

Added

• plan/apply now correct an existing environment's reviewers, not
  just create the environment when it's missing. GitHub's list endpoint
  already returns each environment's required-reviewers rule, so this costs
  no extra request. Reviewers are compared as a set — order is never drift,
  same as topics.
• An environment whose required reviewer is a team is reported as
  blocked rather than corrected: octoform only resolves a declared reviewer
  to a user id, so it has no way to compare against — or safely write over
  — a team's protection. Reading that case as "no reviewers" would have made
  a normal-looking change quietly replace the team the moment apply ran.
• docs/domain-model.md: a diagram of the actual
  types behind plan() — what's declared, what's observed, and the Change
  produced by comparing them.

Changed

• Breaking (type-level): RepoStructure.environments is now
  ExistingEnvironment[] ({ name, reviewers }) instead of string[]. Only
  affects programmatic use of getRepoDetail's return value directly — the
  CLI and octoform.yml are unaffected.