installPackage does not create or update the info dir index beside the .info file it writes

Nobody has claimed this yet.

This issue was triaged from [`bugs/dan/1-application-dir-info-dir`](https://github.com/Macaulay2/M2/blob/388c1ff0ce30d83751dea7bc7eac77fdc1305dd7/bugs/dan/1-application-dir-info-dir), 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
installPackage should create and update "dir", too

/Users/dan/Library/Application Support/Macaulay2/local/share/info:
total used in directory 8 available 128477364
drwxr-xr-x 3 dan staff 102 Jul 16 15:12 .
drwxr-xr-x 5 dan staff 170 Jul 16 14:48 ..
-rw-r--r-- 1 dan staff 3919 Jul 16 15:12 OpenMath.info
```

### Where it stands today

Still not done. `installPackage` writes an `.info` file into the user's Application Support tree but
never creates or updates the `dir` index beside it.

### What that costs the user

Info readers find pages through `dir`. Without it, a package's info documentation is on disk and
unreachable by the normal route — the user has to know the file name and open it directly.

### Where `install-info` does and does not appear

It appears in `cmake/packaging.cmake`, for the deb and rpm builds, and in `configure.ac` as a build-time
requirement. Nothing on the `installPackage` path calls it. So the *system* install has its index
maintained (on Debian by dpkg's `interest-noawait /usr/share/info` trigger, which is why the packaging
needs no scriptlet), and the *user* install does not.

### Notes for whoever picks this up

`setup()` already knows about this directory — `files.m2:432,443` prepends the layout's info directory to
`INFOPATH` — so the location is available; what is missing is running `install-info` (or writing an
equivalent index) after the `.info` file is generated. Two other rows in the catalogue point here for the
same reason.

_{`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 reading files.m2 around lines 432 and 443, where setup() configures the info directory, then trace the installPackage path that generates the .info file. Compare the existing install-info references in cmake/packaging.cmake and configure.ac. Done means the user’s info directory has a created or updated dir index beside the installed .info file.

Written by the indexing model from the issue text.