This PR adds a `result? : Option TraceResult` field to `TraceData` and
populates it in `withTraceNode` and `withTraceNodeBefore`, so that
metaprograms walking trace trees can determine success/failure
structurally instead of string-matching on emoji.
`TraceResult` has three cases: `.success` (checkEmoji), `.failure`
(crossEmoji), and `.error` (bombEmoji, exception thrown). An
`ExceptToTraceResult` typeclass converts `Except` results to
`TraceResult` directly, with instances for `Bool` and `Option`.
`TraceResult.toEmoji` converts back to emoji for display. This replaces
the previous `ExceptToEmoji` typeclass — `TraceResult` is now the
primary representation rather than being derived from emoji strings.
`withTraceNodeBefore` (used by `isDefEq`) uses
`ExceptToTraceResult.toTraceResult` directly, correctly handling `Bool`
(`.ok false` = failure) and `Option` (`.ok none` = failure), with
`Except.error` mapping to `.error`.
For `withTraceNode`, `result?` defaults to `none`. Callers can pass
`mkResult?` to provide structured results; when set, the corresponding
emoji is auto-prepended to the message.
Motivated by mathlib's `#defeq_abuse` diagnostic tactic
(https://github.com/leanprover-community/mathlib4/pull/35750) which
currently string-matches on emoji to determine trace node outcomes. See
https://leanprover.zulipchat.com/#narrow/channel/113488-general/topic/backward.2EisDefEq.2ErespectTransparency🤖 Prepared with Claude Code
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
This PR migrates most remaining tests to the new test suite. It also
completes the migration of directories like `tests/lean/run`, meaning
that PRs trying to add tests to those old directories will now fail.
