agy uses different resume syntax than claude: -c/--continue always
resumes the most-recent session, while --conversation takes a
specific session id. Previously -r/--resume was blanket-mapped to
-c/--continue, breaking `agy --resume <id>` and `agy -r=<id>` style
invocations. Now bare -r/--resume (no id following) maps to
-c/--continue; -r/--resume given an id (via =id or a following
non-flag word) maps to --conversation(=id).