fix(cli): install codex CLI in codex template Dockerfiles

Address Greptile review: the default, sync and temporal codex Dockerfiles
installed nodejs/npm but never the codex CLI, so scaffolded containers hit
FileNotFoundError on `codex` for every request. Add
`npm install -g @openai/codex`, matching the claude-code templates.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: declan-scale

src/agentex/lib/cli/templates/default-codex/Dockerfile.j2

@@ -20,6 +20,10 @@ RUN apt-get update && apt-get install -y \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
+# Install the codex CLI: the agent shells out to `codex` on every turn, so the
+# binary must be present in the runtime image.
+RUN npm install -g @openai/codex
+
 RUN uv pip install --system --upgrade pip setuptools wheel
 
 ENV UV_HTTP_TIMEOUT=1000

src/agentex/lib/cli/templates/sync-codex/Dockerfile.j2

@@ -20,6 +20,10 @@ RUN apt-get update && apt-get install -y \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
+# Install the codex CLI: the agent shells out to `codex` on every turn, so the
+# binary must be present in the runtime image.
+RUN npm install -g @openai/codex
+
 RUN uv pip install --system --upgrade pip setuptools wheel
 
 ENV UV_HTTP_TIMEOUT=1000

src/agentex/lib/cli/templates/temporal-codex/Dockerfile.j2

@@ -20,6 +20,10 @@ RUN apt-get update && apt-get install -y \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
+# Install the codex CLI: the activity shells out to `codex` on every turn, so
+# the binary must be present in the runtime image.
+RUN npm install -g @openai/codex
+
 # Install tctl (Temporal CLI)
 RUN ARCH="$(uname -m)" && \
     case "$ARCH" in x86_64) TCTL_ARCH=amd64 ;; aarch64|arm64) TCTL_ARCH=arm64 ;; *) TCTL_ARCH=amd64 ;; esac && \