Default repo-memory should be qualified by workflow name

[dsyme]

The repo memory feature uses memory/default branch by default. But better to qualifiy the branch by the workflow name, e.g. memory/repo-assist

For those who don't know about repo memory it's here https://github.github.com/gh-aw/reference/repo-memory/

Example memory state https://github.com/fsprojects/FSharp.Control.AsyncSeq/blob/memory/default/state.json

[pelikhan]

Use workflow id to mangle the repo branch, not the name