docs(model): re-verify Nemotron 3.5 Lightning training at a recipe-containing revision

The Lightning card's training leaves were pinned to bridge_commits that
predate the recipe rename in #5303, so the recipes named in their
published commands did not exist at the recorded revision.

Move the card default bridge_commit to bcd2d13 (#5303), keep the
conversion and inference items at 619a2df with explicit pins, drop the
per-leaf training pins, and replace the re-run training leaves' metrics
and expected results with values measured in nvcr.io/nvidia/nemo:26.08 at
bcd2d13 on 2x8 H100 and 2x4 GB200. The H100 long-context SFT leaf is
re-run in the following commit.

Add a doc-consistency test that each verified Lightning recipe exists at
the revision its leaf records.

Signed-off-by: Pruthviraj Prakash <pruprakash@nvidia.com>

Author: pruprakash