feat(cli): add --new flag to start new omp session

dot_local/bin/executable_omp-session

@@ -20,11 +20,13 @@ Cable entry points:
   omp-session --list          one "display<TAB>session file" record per session
   omp-session --preview FILE  title, cwd, and the conversation's message text
   omp-session --resume FILE   the cable's enter action: `omp --resume FILE`
+  omp-session --new           the cable's ctrl-n action: a new `omp` session
 
 Env:
-  OMP_SESSION_STATE=FILE  --resume writes `ran` to it, so the launcher can tell
-                          a resumed session from a cancelled picker and only
-                          move the cursor back up after a cancel (tv --inline).
+  OMP_SESSION_STATE=FILE  --resume/--new write `ran` to it, so the launcher can
+                          tell a started session from a cancelled picker and
+                          only move the cursor back up after a cancel (tv
+                          --inline).
   PI_CODING_AGENT_DIR     omp's agent dir (default ~/.omp/agent).
 """
 
@@ -219,10 +221,14 @@ def cmd_preview(path):
                 print(f"\n{colors[role]}▌ {role}\033[0m\n{text}")
 
 
-def cmd_resume(path):
+def mark_ran():
     state = os.environ.get("OMP_SESSION_STATE")
     if state:
         Path(state).write_text("ran\n")
+
+
+def cmd_resume(path):
+    mark_ran()
     os.execvp("omp", ["omp", "--resume", str(path)])
 
 
@@ -230,6 +236,7 @@ def cmd_resume(path):
 
 
 def new_session():
+    mark_ran()
     os.execvp("omp", ["omp"])
 
 
@@ -279,8 +286,10 @@ def main(argv):
         cmd_preview(argv[1])
     elif argv[0] == "--resume" and len(argv) == 2:
         cmd_resume(argv[1])
+    elif argv == ["--new"]:
+        new_session()
     else:
-        sys.exit("usage: omp-session [--list | --preview FILE | --resume FILE]")
+        sys.exit("usage: omp-session [--list | --preview FILE | --resume FILE | --new]")
 
 
 if __name__ == "__main__":