[Doc] Add layer_sharding additional config for DeepSeek-V3.2-W8A8 (#5921)

### What this PR does / why we need it?

#### Documentation Improvements

New Configuration: Added the layer_sharding parameter to the
DeepSeek-V3.2-W8A8 deployment tutorial. This guides users to include
`["q_b_proj", "o_proj"]` in their prefill node setup for better resource
utilization.

#### CI and Testing Updates

Test Config Update: Updated the multi-node E2E test configuration file:
tests/e2e/nightly/multi_node/config/DeepSeek-V3_2-W8A8-A3-dual-nodes.yaml.

including disable `FLASHCOMM` and enable `FULL_DECODE_ONLY` and update
performance baseline.

### Does this PR introduce any user-facing change?

Yes. The documentation now recommends a more optimized startup command
for DeepSeek-V3.2-W8A8. Users following the updated tutorial will see
improved performance in multi-node PD disaggregation environments.

### How was this patch tested?
CI Validation: The updated E2E test configuration has been verified
through the nightly CI pipeline.

Environment: * vLLM version: v0.13.0

Base Commit:
[11b6af5](11b6af5280)

Hardware: Ascend A3/A2 multi-node cluster.

---------

Signed-off-by: guozr <guozr1997@hotmail.com>
Co-authored-by: guozr <guozr1997@hotmail.com>

docs/source/tutorials/DeepSeek-V3.2.md

@@ -313,6 +313,7 @@ Before you start, please
             --quantization ascend \
             --enforce-eager \
             --no-enable-prefix-caching \
+            --additional-config '{"layer_sharding": ["q_b_proj", "o_proj"]}' \
             --kv-transfer-config \
             '{"kv_connector": "MooncakeConnectorV1",
             "kv_role": "kv_producer",
@@ -388,6 +389,7 @@ Before you start, please
             --quantization ascend \
             --enforce-eager \
             --no-enable-prefix-caching \
+            --additional-config '{"layer_sharding": ["q_b_proj", "o_proj"]}' \
             --kv-transfer-config \
             '{"kv_connector": "MooncakeConnectorV1",
             "kv_role": "kv_producer",