Make tool bin executable if not set from tarball

**Is your feature request related to a problem? Please describe.**

If the distributor of a tool does not ship the tool bin with executable bit set or in other circumstances, the install will fail because of the missing permission bit. A plugin developer has to add a `chmod +x` on its own, instead of the template already taking this burden.

**Describe the solution you'd like**

Instead of creating chore work, maybe not fail when exec perm check fails, but try to set `+x` first. If the file itself is missing due to a failed install, it will still fail, which seems fine.

**Describe alternatives you've considered**

Let every plugin dev stumble over package maintainers not setting an exec bit and re-iterate with adding a `chmod`.

Start by locating the template's install path and the executable-permission check for tool binaries extracted from tarballs. Confirm how a missing executable bit is handled, then verify that installation sets it before the check while still failing when the file itself is missing.

Written by the indexing model from the issue text.