refactor: normalize logging to use %-style formatting

Convert f-string logging to lazy %-style interpolation throughout:
- session_manager.py
- cli.py
- terminal_session.py

This follows Python logging best practices for performance (lazy
evaluation) and consistency across the codebase.

Addresses REFACTORING.md item about normalizing logging style.

src/textual_webterm/cli.py

@@ -139,7 +139,7 @@ def app(
         textual-webterm -a ./calculator.py:CalculatorApp  # Serve from file
     """
     VERSION = version("textual-webterm")
-    log.info(f"textual-webterm v{VERSION}")
+    log.info("textual-webterm v%s", VERSION)
 
     if constants.DEBUG:
         log.warning("DEBUG env var is set; logs may be verbose!")
@@ -184,10 +184,10 @@ def app(
         else:
             # Module path - validate module and class names
             if not module_part.replace(".", "").replace("_", "").isalnum():
-                log.error(f"Invalid module path: {module_part}")
+                log.error("Invalid module path: %s", module_part)
                 sys.exit(1)
             if not class_name.isidentifier():
-                log.error(f"Invalid class name: {class_name}")
+                log.error("Invalid class name: %s", class_name)
                 sys.exit(1)
             run_command = (
                 f'python3 -c "from {module_part} import {class_name}; {class_name}().run()"'
@@ -195,16 +195,16 @@ def app(
 
         app_name = getattr(app_class, "TITLE", None) or class_name
         server.add_app(app_name, run_command, "")
-        log.info(f"Serving Textual app: {app_path}")
+        log.info("Serving Textual app: %s", app_path)
     elif command:
         # Run command as terminal
         server.add_terminal("Terminal", command, "")
-        log.info(f"Serving terminal: {command}")
+        log.info("Serving terminal: %s", command)
     elif not landing_apps:
         # Run default shell
         terminal_command = os.environ.get("SHELL", "/bin/sh")
         server.add_terminal("Terminal", terminal_command, "")
-        log.info(f"Serving terminal: {terminal_command}")
+        log.info("Serving terminal: %s", terminal_command)
 
     def _run_async():
         if constants.WINDOWS:

src/textual_webterm/session_manager.py

@@ -59,7 +59,7 @@ class SessionManager:
         route_key = self.routes.get_key(session_id)
         if route_key is not None:
             del self.routes[route_key]
-        log.debug(f"Session {session_id} ended")
+        log.debug("Session %s ended", session_id)
 
     async def close_all(self, timeout: float = 3.0) -> None:
         """Close app sessions.
@@ -132,20 +132,20 @@ class SessionManager:
                     session_id,
                     app.command,
                 )
-                log.info(f"Created terminal session {session_id}")
+                log.info("Created terminal session %s", session_id)
         else:
             session_process = AppSession(
                 self.path,
                 app.command,
                 session_id,
             )
-            log.info(f"Created app session {session_id}")
+            log.info("Created app session %s", session_id)
 
         self.sessions[session_id] = session_process
         self.routes[route_key] = session_id
 
         await session_process.open(*size)
-        log.debug(f"Session {session_id} opened and ready")
+        log.debug("Session %s opened and ready", session_id)
 
         return session_process
 

src/textual_webterm/terminal_session.py

@@ -54,7 +54,7 @@ class TerminalSession(Session):
         yield "command", self.command
 
     async def open(self, width: int = 80, height: int = 24) -> None:
-        log.info(f"Opening terminal session {self.session_id} with command: {self.command}")
+        log.info("Opening terminal session %s with command: %s", self.session_id, self.command)
         pid, master_fd = pty.fork()
         self.pid = pid
         self.master_fd = master_fd
@@ -78,7 +78,7 @@ class TerminalSession(Session):
             os.close(master_fd)
             self.master_fd = None
             raise
-        log.debug(f"Terminal session {self.session_id} opened successfully")
+        log.debug("Terminal session %s opened successfully", self.session_id)
 
     def _set_terminal_size(self, width: int, height: int) -> None:
         buf = array.array("h", [height, width, 0, 0])
@@ -106,7 +106,7 @@ class TerminalSession(Session):
     def update_connector(self, connector: SessionConnector) -> None:
         """Update the connector for reconnection without restarting the session."""
         self._connector = connector
-        log.debug(f"Updated connector for session {self.session_id}")
+        log.debug("Updated connector for session %s", self.session_id)
 
     async def start(self, connector: SessionConnector) -> asyncio.Task:
         self._connector = connector
@@ -158,7 +158,7 @@ class TerminalSession(Session):
             except ProcessLookupError:
                 pass  # Process already gone
             except Exception as e:
-                log.warning(f"Error closing terminal session {self.session_id}: {e}")
+                log.warning("Error closing terminal session %s: %s", self.session_id, e)
 
     async def wait(self) -> None:
         if self._task is not None: