agentic: install git on-demand for aiperf editable install

vllm/vllm-openai:v0.21.0-ubuntu2404 ships without git, but pip's
editable install (-e) of utils/aiperf invokes `git version` to record
direct_url.json provenance. Without git, every R16 shard on both
gb300-nv and gb300-cw failed at:

    + python3 -m pip install --break-system-packages -q --ignore-installed -e /infmax-workspace/utils/aiperf
      ERROR: Error [Errno 2] No such file or directory: 'git' while executing command git version
      ERROR: Cannot find command 'git' - do you have 'git' installed and in your PATH?

This happens AFTER server boot is healthy and "Server is healthy - starting
benchmark" has fired, so all the upstream cluster/recipe work (preflight,
mem=0 x2 layers, etcd cpus-per-task=72, --no-preflight, /scratch model
path, NixlConnector P<->D, model load) is working end-to-end. Only the
pip install step is blocked.

Fix: prepend a `command -v git || apt-get update && apt-get install -y git`
to install_agentic_deps. Cheap no-op on images that already ship git
(AMD images, custom containers). The vLLM image's apt is functional from
inside the container so this works without container rebuild.

The -e install was introduced yesterday in e92a9bf (aiperf v0.2
migration); previously the agentic flow used kv-cache-tester which
didn't need git.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: cquil11

benchmarks/benchmark_lib.sh

@@ -919,6 +919,16 @@ resolve_trace_source() {
 }
 
 install_agentic_deps() {
+    # vllm/vllm-openai container ships without git, but pip's editable
+    # install (-e) of the aiperf submodule below invokes `git version`
+    # to record direct_url.json provenance and bails if git is missing:
+    #   ERROR: Cannot find command 'git' - do you have 'git' installed
+    #   and in your PATH?
+    # Install on demand; cheap no-op when git is already present
+    # (e.g. on AMD images that ship it).
+    if ! command -v git >/dev/null 2>&1; then
+        apt-get update -qq && apt-get install -y -qq git
+    fi
     agentic_pip_install --quiet urllib3 requests 2>/dev/null || true
     agentic_pip_install -q -r "$AGENTIC_DIR/requirements.txt"
     # Editable install of aiperf from the submodule — gives us the