Documentation html filenames still contain raw UTF-8

Nobody has claimed this yet.

This issue was triaged from [`bugs/dan/0-utf-8-in-doc-filenames`](https://github.com/Macaulay2/M2/blob/388c1ff0ce30d83751dea7bc7eac77fdc1305dd7/bugs/dan/0-utf-8-in-doc-filenames), one of the 857 files removed from the pre-GitHub `bugs/` tree by [`d2c8d27826`](https://github.com/Macaulay2/M2/commit/d2c8d27826) and catalogued in [#36](https://github.com/Macaulay2/M2/issues/36). **The commentary below was written by Claude (Claude Opus 5, via Claude Code)**, not by @d-torrance, whose account posted it -- please weigh it accordingly.

### The original file, verbatim

```text
-*- coding: utf-8 -*-

oops, we allowed utf-8 to creep into a file name:

~/to/Macaulay2/doc/Macaulay2-1.2/share/doc/Macaulay2/Macaulay2Doc/html/___Gröbner_spbases.html
```

### Where it stands today

Still generated. `toFilename` maps the ASCII specials through its `tt` table but passes multi-byte
UTF-8 through unchanged, so the installed documentation holds **9 such names**, including the exact one
this file names:

```
share/doc/Macaulay2/Macaulay2Doc/html/___Gröbner_spbases.html
```

### Two closed issues are the same cause, not the same ask

Worth spelling out, because a search turns them up and they look like duplicates:

- **#47** covered this and closed in 2014 on the broken *links*, not on the filename question.
- **#211** is a second symptom of the same cause — the file appearing under two different UTF-8
normalizations (`303 266` vs `314 210`) — closed on *"just remember how I do it and check that one
file"*.

So neither settled the ask, which is why the file was still worth filing.

### Why it matters beyond tidiness

A non-ASCII filename is a portability and normalization hazard rather than an aesthetic one: it is what
produced #211's two spellings of the same page, and it constrains any filesystem or archive format in
the distribution chain that is not UTF-8 clean.

_{`open` · disposition `issue` · source of truth: [`bug-triage/catalog.tsv`](https://github.com/d-torrance/M2/blob/bug-triage/bug-triage/catalog.tsv)}

Start by locating the toFilename entry point and inspecting its tt table, then examine the generated names under share/doc/Macaulay2/Macaulay2Doc/html/. Compare the nine names containing raw UTF-8, including ___Gröbner_spbases.html, and trace where those names are produced. Done means generated documentation filenames no longer contain raw UTF-8 while their links remain usable.

Written by the indexing model from the issue text.