Upgrading the scaffold

stayfixed upgrade moves [stayfixed] version to the stayfixed running and refreshes every
scaffold file whose bytes are still the ones stayfixed wrote. When the workflow pins stayfixed by
commit, [ci] ref and the workflow's pin move with the version: all three, or none. A file the
user edited is skipped and named, never overwritten.

1. Run stayfixed upgrade --dry-run and relay what it prints: the opening line, the
   stayfixed.toml: line with each key it would move, the scaffold: report with each file's
   verdict, the CI: line, and every note: line.
2. For each file reported skip_modified, edited by the user or never written by stayfixed, ask
   whether the user wants it overwritten. Only on a yes for that file, add --force <path> for
   it, with the path exactly as the report prints it. Never force a path the user did not name.
3. If any --force was added, run stayfixed upgrade --dry-run again with the same flags and
   relay the new report, so the user sees what forcing changes before anything is written.
4. Run stayfixed upgrade with the same flags, and relay the real run's report the same way.
5. Ask the user to commit stayfixed.toml, .stayfixed/manifest.json and the changed files
   together.

Rules

• An exit of 1 wrote nothing. A REFUSED section names each artifact and why. Relay every
  line and stop.
• An exit of 2 is a refusal, and it may have come part-way through. A refusal about the
  project itself — not initialised, no stayfixed.toml, a newer, unreadable or unordered
  recorded version, a key written in a shape it will not edit — comes before any write. One that
  says a file cannot be written comes while writing: what was done before it is on disk and recorded.
  Relay it as printed, run git status to show the user what changed, and after they fix the
  cause run stayfixed upgrade --dry-run again, which plans from what is there now. When it
  says the project records a newer stayfixed than the one running, the plugin is what needs
  updating: relay that, and never edit [stayfixed] version to get past it.
• A note: saying [stayfixed] version and [ci] ref were left as they are is not a
  failure. The scaffold was still refreshed, and the note says what would let the three move
  together. Relay it as printed. When the workflow is reported skip_modified, forcing it is
  step 2's question like any other file's.
• A [ci] ref that is not a commit, such as v1, is the user's choice. Only the version
  moves and the workflow is left as it is. Relay the CI: line, and never change the ref.
• stayfixed.toml keeps every byte but the values it moves. If the command refuses to
  rewrite a key because of how the file writes it, relay the refusal: it names the key and the
  value to set by hand.
• A note: about records this stayfixed does not produce is not an error. Those files were
  left where they are, on purpose.
• A file kept out of git is refreshed only while it holds what stayfixed last wrote there.
  One that changed since is skipped like an edited file, because nothing brings it back once it
  is overwritten. A copy left behind where the artifact no longer goes (its id left
  [artifacts] local, or its [paths] value moved) is removed as relocated while it holds
  those bytes, and skipped once it changed. Ask before forcing a skipped one, like any other.
• A refusal saying git ignores files at a place a [paths] value chose wrote nothing. Relay
  it with the files it names. Pointing that key at a path git does not ignore, or taking it out,
  is the user's decision; never edit stayfixed.toml or an ignore file to get past it.
• A target printed as <id> is one the manifest recorded outside the path grammar. Relay it
  as printed, and never look up or guess the path behind it.
• There are no hooks to re-trust. init writes no project-level hook entries, so an upgrade
  changes none.