feat: --pass-session-id flag to include session ID in system prompt

Adds --pass-session-id CLI flag that includes the session ID in the
agent's system prompt when set:

  hermes --pass-session-id
  hermes chat --pass-session-id

Sets HERMES_PASS_SESSION_ID=1 env var, which _build_system_prompt()
checks before appending the session ID.

hermes_cli/main.py

@@ -203,6 +203,10 @@ def cmd_chat(args):
     except Exception:
         pass
 
+    # --pass-session-id: include session ID in the agent's system prompt
+    if getattr(args, "pass_session_id", False):
+        os.environ["HERMES_PASS_SESSION_ID"] = "1"
+
     # Import and run the CLI
     from cli import main as cli_main
     
@@ -1303,6 +1307,12 @@ For more help on a command:
         default=False,
         help="Run in an isolated git worktree (for parallel agents)"
     )
+    parser.add_argument(
+        "--pass-session-id",
+        action="store_true",
+        default=False,
+        help="Include the session ID in the agent's system prompt"
+    )
     
     subparsers = parser.add_subparsers(dest="command", help="Command to run")
     
@@ -1357,6 +1367,12 @@ For more help on a command:
         default=False,
         help="Run in an isolated git worktree (for parallel agents on the same repo)"
     )
+    chat_parser.add_argument(
+        "--pass-session-id",
+        action="store_true",
+        default=False,
+        help="Include the session ID in the agent's system prompt"
+    )
     chat_parser.set_defaults(func=cmd_chat)
 
     # =========================================================================

run_agent.py

@@ -1409,9 +1409,10 @@ class AIAgent:
 
         from hermes_time import now as _hermes_now
         now = _hermes_now()
-        prompt_parts.append(
-            f"Conversation started: {now.strftime('%A, %B %d, %Y %I:%M %p')}"
-        )
+        timestamp_line = f"Conversation started: {now.strftime('%A, %B %d, %Y %I:%M %p')}"
+        if self.session_id and os.getenv("HERMES_PASS_SESSION_ID"):
+            timestamp_line += f"\nSession ID: {self.session_id}"
+        prompt_parts.append(timestamp_line)
 
         platform_key = (self.platform or "").lower().strip()
         if platform_key in PLATFORM_HINTS: