Add startup session name flag

closes #5153

packages/coding-agent/docs/sessions.md

@@ -10,6 +10,7 @@ Sessions auto-save to `~/.pi/agent/sessions/`, organized by working directory. E
 pi -c                  # Continue most recent session
 pi -r                  # Browse and select from past sessions
 pi --no-session        # Ephemeral mode; do not save
+pi --name "my task"    # Set session display name at startup
 pi --session <path|id> # Use a specific session file or partial session ID
 pi --fork <path|id>    # Fork a session file or partial session ID into a new session
 ```
@@ -56,6 +57,13 @@ Use `/name <name>` to set a human-readable session name:
 /name Refactor auth module
 ```
 
+Set the name at startup with `--name` or `-n`:
+
+```bash
+pi --name "Refactor auth module"
+pi --name "CI audit" -p "Review this build failure"
+```
+
 Named sessions are easier to find in `/resume` and `pi -r`.
 
 ## Branching with `/tree`