Log forward port followup to chatter

[xmo-odoo]

Currently the forward-port decisions are only logged to, well, the log. Which is very opaque and hard to access (even for me).

It might be a good idea to log it to the source PRs or the chatter (possibly adding a batch chatter for that? would allow tracking batch shit too). One probable limitation in that case is that "wrong state" keeps running possibly forever, so would have to be modified / handled specially in order not to make this a pain in the ass...

Alternatively there could be a special signal to handle this and avoid even trying to schedule followups for PRs or batches which can't have changed (so probably gate _validate to first check the pr / batch state).