feat: support bundled frame-window offsets in zed_svo_to_mcap

Implement bundled multi-camera --start-frame semantics as synced-group\nindices from the common synced start, inclusive with --end-frame.\n\nUpdate zed_svo_to_mcap to skip synced groups before writing, keep\nsingle-camera raw SVO frame semantics unchanged, and adjust exact\nprogress totals for selected bundled windows.\n\nReplace the expensive bundled exact pre-count path with approximate\ntime-window progress when --end-frame is not set, and update the\nshared TTY progress bar helper to support fraction-based rendering.\n\nExpose --start-frame in the batch MCAP wrapper and document the\nbundled frame-window semantics and approximate progress behavior in\nthe README.

scripts/zed_batch_svo_to_mcap.py

@@ -37,6 +37,7 @@ class BatchConfig:
     with_pose: bool
     pose_config: Path | None
     world_frame_id: str | None
+    start_frame: int | None
     end_frame: int | None
     sync_tolerance_ms: float | None
 
@@ -293,6 +294,8 @@ def command_for_job(job: ConversionJob, config: BatchConfig) -> list[str]:
         command.extend(["--pose-config", str(config.pose_config)])
     if config.world_frame_id is not None:
         command.extend(["--world-frame-id", config.world_frame_id])
+    if config.start_frame is not None:
+        command.extend(["--start-frame", str(config.start_frame)])
     if config.end_frame is not None:
         command.extend(["--end-frame", str(config.end_frame)])
     if config.sync_tolerance_ms is not None:
@@ -576,6 +579,12 @@ def run_batch(jobs: list[ConversionJob], config: BatchConfig, jobs_limit: int) -
     default=None,
     help="Optional pose reference frame id passed through to zed_svo_to_mcap.",
 )
+@click.option(
+    "--start-frame",
+    type=click.IntRange(min=0),
+    default=None,
+    help="First synced frame group to export (inclusive) in bundled multi-camera mode.",
+)
 @click.option(
     "--end-frame",
     type=click.IntRange(min=0),
@@ -609,6 +618,7 @@ def main(
     with_pose: bool,
     pose_config: Path | None,
     world_frame_id: str | None,
+    start_frame: int | None,
     end_frame: int | None,
     sync_tolerance_ms: float | None,
 ) -> None:
@@ -631,6 +641,7 @@ def main(
         with_pose=with_pose,
         pose_config=pose_config.expanduser().resolve() if pose_config is not None else None,
         world_frame_id=world_frame_id,
+        start_frame=start_frame,
         end_frame=end_frame,
         sync_tolerance_ms=sync_tolerance_ms,
     )