Add custom SVG exporter, remove Rich from screenshot rendering

- Created svg_exporter.py with direct pyte-to-SVG rendering
- Eliminates Rich's export_svg() quirks (clip path count mismatch)
- Added 63 comprehensive tests for SVG exporter
- Removed Rich imports from local_server.py, terminal_session.py,
  app_session.py, and cli.py
- Replaced RichHandler with standard logging.basicConfig
- Replaced @rich.repr.auto with standard __repr__ methods
- Rich is no longer directly imported (still transitive via textual-serve)

Bump version to 0.3.0

src/textual_webterm/app_session.py

@@ -11,7 +11,6 @@ from enum import Enum, auto
 from time import monotonic
 from typing import TYPE_CHECKING
 
-import rich.repr
 from importlib_metadata import version
 
 from . import constants
@@ -41,7 +40,6 @@ class ProcessState(Enum):
         return self.name
 
 
-@rich.repr.auto(angular=True)
 class AppSession(Session):
     """Runs a single app process."""
 
@@ -128,11 +126,9 @@ class AppSession(Session):
         """Check if the app session is still running."""
         return self._state == ProcessState.RUNNING
 
-    def __rich_repr__(self) -> rich.repr.Result:
-        yield self.command
-        yield "id", self.session_id
-        if self._process is not None:
-            yield "returncode", self._process.returncode, None
+    def __repr__(self) -> str:
+        returncode = self._process.returncode if self._process else None
+        return f"<AppSession {self.command!r} id={self.session_id!r} returncode={returncode}>"
 
     async def open(self, width: int = 80, height: int = 24) -> None:
         """Open the process."""