`/usr/local/bin` symlinks are non-functional

(Via https://github.com/Witiko/markdown/issues/575#issuecomment-3047269655 and https://gitlab.com/islandoftex/images/texlive/-/issues/30)

```console
$ sudo tlmgr path add

$ export PATH=/usr/local/bin/:/usr/bin/

$ mtxrun --generate
resolvers | resolving | variable 'SELFAUTOLOC' set to '/usr/local/bin'
resolvers | resolving | variable 'SELFAUTODIR' set to '/usr/local'
resolvers | resolving | variable 'SELFAUTOPARENT' set to '/usr'
resolvers | resolving | variable 'TEXMFCNF' set to ''
resolvers | resolving | variable 'TEXMF' set to ''
resolvers | resolving | variable 'TEXOS' set to 'local'
resolvers | resolving |
resolvers | resolving | using configuration specification 'home:texmf/web2c;selfautoparent:/texmf-local/web2c;selfautoparent:/texmf-context/web2c;selfautoparent:/texmf/web2c'
resolvers | resolving |
resolvers | resolving | looking for regular 'texmfcnf.lua' on given path '/home/max/texmf/web2c' from specification 'home:texmf/web2c'
resolvers | resolving | looking for regular 'texmfcnf.lua' on given path '/usr/texmf-local/web2c' from specification 'selfautoparent:/texmf-local/web2c'
resolvers | resolving | looking for regular 'texmfcnf.lua' on given path '/usr/texmf-context/web2c' from specification 'selfautoparent:/texmf-context/web2c'
resolvers | resolving | looking for regular 'texmfcnf.lua' on given path '/usr/texmf/web2c' from specification 'selfautoparent:/texmf/web2c'
resolvers | resolving | looking for fallback 'contextcnf.lua' on given path '/home/max/texmf/web2c' from specification 'home:texmf/web2c'
resolvers | resolving | looking for fallback 'contextcnf.lua' on given path '/usr/texmf-local/web2c' from specification 'selfautoparent:/texmf-local/web2c'
resolvers | resolving | looking for fallback 'contextcnf.lua' on given path '/usr/texmf-context/web2c' from specification 'selfautoparent:/texmf-context/web2c'
resolvers | resolving | looking for fallback 'contextcnf.lua' on given path '/usr/texmf/web2c' from specification 'selfautoparent:/texmf/web2c'
resolvers | resolving |
resolvers | resolving | warning: no lua configuration files found
resolvers | resolving | no texmf paths are defined (using TEXMF)
resolvers | resolving |
mtxrun |
mtxrun | elapsed lua time: 0.008 seconds

$ context --once --nofile
mtxrun | forcing cache reload
resolvers | resolving | looking for regular 'texmfcnf.lua' on given path '/home/max/texmf/web2c' from specification 'home:texmf/web2c'
resolvers | resolving | looking for regular 'texmfcnf.lua' on given path '/usr/texmf-local/web2c' from specification 'selfautoparent:/texmf-local/web2c'
resolvers | resolving | looking for regular 'texmfcnf.lua' on given path '/usr/texmf-context/web2c' from specification 'selfautoparent:/texmf-context/web2c'
resolvers | resolving | looking for regular 'texmfcnf.lua' on given path '/usr/texmf/web2c' from specification 'selfautoparent:/texmf/web2c'
resolvers | resolving | looking for fallback 'contextcnf.lua' on given path '/home/max/texmf/web2c' from specification 'home:texmf/web2c'
resolvers | resolving | looking for fallback 'contextcnf.lua' on given path '/usr/texmf-local/web2c' from specification 'selfautoparent:/texmf-local/web2c'
resolvers | resolving | looking for fallback 'contextcnf.lua' on given path '/usr/texmf-context/web2c' from specification 'selfautoparent:/texmf-context/web2c'
resolvers | resolving | looking for fallback 'contextcnf.lua' on given path '/usr/texmf/web2c' from specification 'selfautoparent:/texmf/web2c'
resolvers | resolving |
resolvers | resolving | warning: no lua configuration files found
resolvers | resolving | no texmf paths are defined (using TEXMF)
resolvers | resolving |
mtxrun | the resolver databases are not present or outdated
resolvers | resolving | using suffix based filetype 'lua'
resolvers | resolving | remembering file 'mtx-context.lua' using hash 'lua::mtx-context.lua'
resolvers | resolving | using suffix based filetype 'lua'
resolvers | resolving | remembering file 'mtx-contexts.lua' using hash 'lua::mtx-contexts.lua'
resolvers | resolving | remembered file 'mtx-context.lua'
resolvers | resolving | using suffix based filetype 'lua'
resolvers | resolving | remembering file 'mtx-t-mtx-context.lua' using hash 'lua::mtx-t-mtx-context.lua'
resolvers | resolving | using suffix based filetype 'lua'
resolvers | resolving | remembering file 'mtx-t-mtx-contexts.lua' using hash 'lua::mtx-t-mtx-contexts.lua'
resolvers | resolving | remembered file 'mtx-t-mtx-context.lua'
resolvers | resolving | remembered file 'mtx-context.lua'
mtxrun | unknown script 'mtx-context.lua' or 'mtx-mtx-context.lua'
```

This is a mess and will need a patch in `mtxrun.lua` to follow symlinks as needed.

Start with mtxrun.lua and reproduce the failure using tlmgr path add, the shown PATH, mtxrun --generate, and context --once --nofile. Trace how the executable location is resolved through the /usr/local/bin symlinks; done means these commands find the ConTeXt scripts and no longer report missing Lua configuration or unknown scripts.

Written by the indexing model from the issue text.