fix(postCreate): graceful handling when .git is missing

If the user opens the devcontainer before running `git init`, uv sync
fails opaquely because setuptools-scm can't compute a version. VS
Code's wrapper hides the real stderr, leaving an exit-1 stack trace
with no clue about the cause.

postCreate.sh now detects a missing .git directory, prints a clear
warning explaining what's happening, falls back to
SETUPTOOLS_SCM_PRETEND_VERSION_FOR_<DIST>=0.0.0 so uv sync finishes,
and skips pre-commit install (which needs .git/hooks). Once the user
runs `git init && git add . && git commit`, re-running the script
picks up the real version from git automatically.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: gilesknap

template/.devcontainer/postCreate.sh.jinja

@@ -4,15 +4,44 @@ set -euo pipefail
 # Install Claude Code CLI
 curl -fsSL https://claude.ai/install.sh | bash
 {% endif %}
+# setuptools-scm derives the package version from git tags, and
+# pre-commit installs its hooks into .git/hooks. If the project hasn't
+# been `git init`-ed yet, fall back to a pretend version so `uv sync`
+# can finish, skip the hook install, and tell the user how to switch
+# to a real setup. Subsequent `uv sync` runs (after `git init` and a
+# commit) will recompute the real version from git automatically.
+if [ ! -d .git ]; then
+    cat <<'EOF'
+
+================================================================
+WARNING: This directory is not a git repository.
+
+  - Using SETUPTOOLS_SCM_PRETEND_VERSION_FOR_{{ distribution_name | replace('-', '_') | replace('.', '_') | upper }}=0.0.0
+    so `uv sync` can finish without setuptools-scm failing.
+  - Skipping `pre-commit install` (it needs .git/hooks).
+
+To get a real version and pre-commit hooks, run later:
+
+    git init && git add . && git commit -m 'Initial commit'
+    .devcontainer/postCreate.sh
+
+================================================================
+
+EOF
+    export SETUPTOOLS_SCM_PRETEND_VERSION_FOR_{{ distribution_name | replace('-', '_') | replace('.', '_') | upper }}=0.0.0
+fi
+
 # Install Python dependencies and pre-commit hooks
 uv venv --clear
 uv sync
-pre-commit install --install-hooks
+if [ -d .git ]; then
+    pre-commit install --install-hooks
+fi
 
 # Init only submodules that aren't checked out yet — first-clone
 # protection without touching already-initialized submodules (which
 # would yank in-progress branch work to detached HEAD on rebuild).
-if [ -f .gitmodules ]; then
+if [ -d .git ] && [ -f .gitmodules ]; then
     missing=$(git submodule status | awk '/^-/ {print $2}')
     [ -n "$missing" ] && git submodule update --init $missing
 fi