v0.7.0

Nothing a corpus resolves to changes. Every command's output is
byte-identical to 0.6.0 — verified across the six conformance corpora and
four real ones, text and JSON, exit codes included. This release is about
the shape of the code and of the published API.

Fixed

• A failure could be reported as an answer. Verdict::Internal
  carried exit 3 — a failure code — inside an enum whose every other
  variant is a verdict, so "the tool broke" and "here is what was
  decided" were the same type. Every caller had to remember a variant
  meaning the opposite of its siblings, and the MCP surface did not: an
  inconsistent graph would have come back isError: false, against the
  rule §14.1 states. resolve returns Result<Verdict, Inconsistent>
  now, and the old shape is unrepresentable.

  Unreachable on a corpus that loaded, since Layer A rejects the
  replacement cycles that cause it — which is the argument for keeping it
  out of the success type, not for trusting the caller.

• A hand-edited pack could declare both first and replaces. Pack
  parsing never checked, and carried the contradiction into the graph.
  There is nowhere to put it now, so the pack is refused with the rest.

Changed

• aval-core's API is versioned deliberately (§15.1). Structs that
  may gain a field are #[non_exhaustive] with constructors; the enums
  are not, because §14 enumerates the verdicts and their exit codes, so
  adding one is major regardless — and marking them would cost the
  exhaustiveness check that makes an unrendered variant a compile error.

• An entry's lineage is a sum type. first: bool beside
  replaces: Vec<_> admitted four states where the model has two; the
  parser already rejected the other two, so the loose shape carried
  ruled-out states into everything that reads an entry.

• A record id is AdrId, not String. The qualification rule of
  §2.3 lived in a free function callers had to remember; it is on the
  type now.

• LoadError renders itself. Two callers matched its variants to
  build the same message, and a third was about to.

• Lints moved into [workspace.lints], so an editor, a bare
  cargo clippy and CI see one set. unsafe_code is now forbidden
  rather than merely absent.

• heads() makes one pass with a set instead of two allocations and a
  linear scan per candidate; migrate no longer panics on a path ending
  in ..; twenty public types gained Debug.

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What's Changed

• refactor: eight review findings by @fredericrous in #12

Full Changelog: v0.6.0...v0.7.0