## What it does
Flags TeX `\begin{env}` blocks that have no matching `\end{env}` (or vice versa), where `env` is
one of the math environments mdwright tracks (`equation`, `align`, `aligned`, `cases`, `matrix`,
`pmatrix`, `bmatrix`, `vmatrix`, `Vmatrix`, `gather`, `multline`, `split`, and their starred
variants).
## Why
`\begin{align} … \end{align}` and friends are math regions. Like `\[ … \]`, they suspend prose
lint rules and are passed through the formatter verbatim. An unmatched `\begin` leaves the
parser unable to tell where math ends; an unmatched `\end` is almost always a copy-paste error
that will silently break rendering in any math-aware renderer.
## Example (bad)
```markdown
\begin{align}
a + b &= c \\
d - e &= f
```
## Example (good)
```markdown
\begin{align}
a + b &= c \\
d - e &= f
\end{align}
```
## Configuration
- Disable inline: `<!-- mdwright: allow math/unbalanced-env -->`.
- Disable in config: `[lint] ignore = ["math/unbalanced-env"]`.
- Severity: non-advisory.
## References
- mdwright's environment recogniser (`src/stdlib/math_unbalanced_env.rs`).
- amsmath user's guide for the canonical environment list.