Improve output of `asdf version` and `asdf info`

Based on https://michael.stapelberg.ch/posts/2026-04-05-stamp-it-all-programs-must-report-their-version/

We should improve the output of `version` and `info` commands with code like this:

```go
package version

import (
"runtime/debug"
"strings"
)

func readParts() (revision string, modified, ok bool) {
info, ok := debug.ReadBuildInfo()
if !ok {
return "", false, false
}
settings := make(map[string]string)
for _, s := range info.Settings {
settings[s.Key] = s.Value
}
// When built from a local VCS directory, we can use vcs.revision directly.
if rev, ok := settings["vcs.revision"]; ok {
return rev, settings["vcs.modified"] == "true", true
}
// When built as a Go module (not from a local VCS directory),
// info.Main.Version is something like v0.0.0-20230107144322-7a5757f46310.
v := info.Main.Version // for convenience
if idx := strings.LastIndexByte(v, '-'); idx > -1 {
return v[idx+1:], false, true
}
return "", false, false
}

func Read() string {
revision, modified, ok := readParts()
if !ok {
return ""
}
modifiedSuffix := ""
if modified {
modifiedSuffix = " (modified)"
}

return "https://github.com/gokrazy/tools/commit/" + revision + modifiedSuffix
}
```

Locate the Go implementations and tests for the `asdf version` and `asdf info` commands, then compare their current output with the proposed build-information approach. Use the linked article and example as context; done means both commands report the program revision and modified state in the intended output format.

Written by the indexing model from the issue text.