fix(cli): report the actual outcome of tags --add and --remove

[Ruzzgar]

tags --add and tags --remove print that the tag was added or removed no matter what happened. The store already reports whether a row was written or deleted, but Client::add_note_tag and Client::remove_note_tag drop that and only warn! about it, so the command ends up contradicting its own log line:

$ miden-client tags --remove 999
WARN miden_client::sync::tag: Tag 999 wasn't being tracked
Tag 999 removed

$ miden-client tags --add 42
Tag 42 added
$ miden-client tags --add 42
WARN miden_client::sync::tag: Tag 42 is already being tracked
Tag 42 added

Both methods now return that flag instead of logging it, and the CLI prints accordingly:

$ miden-client tags --remove 999
Tag 999 wasn't being tracked
$ miden-client tags --add 42
Tag 42 added
$ miden-client tags --add 42
Tag 42 is already being tracked

The return type change doesn't touch any existing caller, since ? and unwrap() discard the bool, so only tags.rs needed updating. Extended the existing tags test to assert the returned value, and fixed the Store::remove_note_tag doc comment, which described a bool return the method doesn't have.

[igamigo]

Thanks