English rules dated at 2026/06/15 or 2026/06/30 are not compatible with NVDA2026.1.1

This is a reformulate of issue #622, to make scenario more clear.

In tests/Languages/en/intent.rs, there is a test:
```
#[test]
fn intent_prob_x() -> Result<()> {
init_logger();
let expr = "";
test("en", "ClearSpeak", expr, "probability of x")?;
return Ok(());

}
```
Let us name above MathML as mathml_A.

In tests/Languages/en/chemistry.rs, there is a test:
```
#[test]
fn mhchem_barbed_equilibrium() -> Result<()> {
let expr = "";
test_prefs("en", "SimpleSpeak", vec![("Verbosity", "Terse")],
expr, "cap h, 2, gas; plus; cap i, 2, gas; is in equilibrium with, 2, cap h, cap i, gas")?;
return Ok(());

}
```
Let us name above MathML as mathml_B.

We also have
* en rules in NVDA2026.1.1, name as en_rules_2026.1.1
* en rules in main branch dated at 2026/06/15, name as en_rules_0615
* en rules in main branch dated at 2026/06/30, name as en_rules_0630

We also have two libmathcat_py.pyd
* that in NVDA2026.1.1, name as libmathcat_2026.1.1
* that get from [libmathcat_py-64-3.13-win.zip](https://github.com/daisy/MathCATForPython/releases), name as libmathcat_3.13

We use NVDA2026.1.1 as platform to do integration test.

For mathml_A, we have following results:
* libmathcat_2026.1.1 + en_rules_2026.1.1, read out as:`probability of x`
* libmathcat_2026.1.1 + en_rules_0615, read out as:`probability`, and we can not navigating the formula.
* libmathcat_2026.1.1 + en_rules_0630, read out as:`probability`, and we can not navigating the formula.

* libmathcat_3.13 + en_rules_2026.1.1, read out as:`probability of x`
* libmathcat_3.13 + en_rules_0615, read out as:`probability`
* libmathcat_3.13 + en_rules_0630, read out as:`probability`

For mathml_B, we have following results:
* libmathcat_2026.1.1 + en_rules_2026.1.1, read out as:`cap h, 2, gas; plus; cap i, 2, gas; is in equilibrium with, 2, cap h, cap i, gas`
* libmathcat_2026.1.1 + en_rules_0615, read out as:`cap h, 2, gas; plus; cap i, 2, gas; ᾍ2 2, cap h, cap i, gas`, and we can not navigating the formula.
* libmathcat_2026.1.1 + en_rules_0630, read out as:`cap h, 2, gas; plus; cap i, 2, gas; ᾍ2 2, cap h, cap i, gas`, and we can not navigating the formula.

* libmathcat_3.13 + en_rules_2026.1.1, read out as:`cap h, 2, gas; plus; cap i, 2, gas; is in equilibrium with, 2, cap h, cap i, gas`
* libmathcat_3.13 + en_rules_0615, read out as:`cap h, 2, gas; plus; cap i, 2, gas; ᾍ2 2, cap h, cap i, gas`
* libmathcat_3.13 + en_rules_0630, read out as:`cap h, 2, gas; plus; cap i, 2, gas; ᾍ2 2, cap h, cap i, gas`

In summary, both en_rules_0615 and en_rules_0630 are not compatible with libmathcat_2026.1.1(contained in original NVDA2026.1.1) and libmathcat_3.13(contained in libmathcat_py-64-3.13-win.zip). Better libmathcat_py.pyd is in need.

Start with tests/Languages/en/intent.rs and tests/Languages/en/chemistry.rs, especially intent_prob_x and mhchem_barbed_equilibrium, then reproduce the reported NVDA2026.1.1 combinations with the two libmathcat_py.pyd files and dated English rules. Done means the current rules and library produce the expected speech and preserve formula navigation for both MathML examples.

Written by the indexing model from the issue text.