Docs tracking: examples in the almanac

The measured state of this is in [the comment below](https://github.com/asc-community/AngouriMath/issues/585#issuecomment-5252760598), which replaces the checklist that used to be here: it linked two merged pull requests as if they were open work, and marked `MathS.*` done when it is 146 of 194.

Counted from the generated `AngouriMath.xml` of a 2.0.0 build:

| surface | documented members | with `` |
|---|---|---|
| `MathS.*` | 194 | 146 |
| `Entity` and its nodes | 980 | 35 |
| `AngouriMath.Extensions` | 89 | 0 |
| `AngouriMath.Core` | 237 | 3 |
| everything else | 331 | 0 |

In order: `AngouriMath.Extensions` first, since all 89 have a summary and none has an example and it is the shortest path into the library; then `Transformation` and `RewriteRecording`, which are new in 2.0; then the `Entity` operation surface, which wants its own issue rather than a ratio.

The wiki is the other half of the docs and is tracked separately — it is now machine-checked against a build (86 samples, 0 compile errors, 0 output mismatches).

Start with the generated AngouriMath.xml from a 2.0.0 build and the AngouriMath.Extensions surface, where all 89 members have summaries but no examples. Work through Extensions first, then Transformation and RewriteRecording, followed by the Entity operation surface as described. Done means the documented members have examples and the generated counts reflect the completed work; the separately tracked wiki is already machine-checked.

Written by the indexing model from the issue text.