Use build args for git user config

Change git configuration to use Docker build args instead of .env file,
simplifying setup and improving security. This change:
- Removes git config from .env and startup.sh
- Adds GIT_USER_NAME and GIT_USER_EMAIL build args
- Updates documentation for new git config approach
- Improves task logging requirements in CLAUDE.md

The build arg approach provides better isolation and ensures git config is
properly set during image build rather than container runtime.

Dockerfile

@@ -82,16 +82,18 @@ RUN bash -c 'source /app/.env && \
         echo "No Twilio credentials found, skipping MCP configuration"; \
     fi'
 
-# Configure git user during build
-RUN bash -c 'source /app/.env && \
-    if [ -n "$GIT_USER_NAME" ] && [ -n "$GIT_USER_EMAIL" ]; then \
-        echo "Configuring git user: $GIT_USER_NAME <$GIT_USER_EMAIL>" && \
-        git config --global user.name "$GIT_USER_NAME" && \
-        git config --global user.email "$GIT_USER_EMAIL" && \
+# Configure git user during build using host git config
+RUN bash -c '\
+    GIT_NAME=$(git config --global --get user.name 2>/dev/null || echo "") && \
+    GIT_EMAIL=$(git config --global --get user.email 2>/dev/null || echo "") && \
+    if [ -n "$GIT_NAME" ] && [ -n "$GIT_EMAIL" ]; then \
+        echo "Configuring git user from host: $GIT_NAME <$GIT_EMAIL>" && \
+        git config --global user.name "$GIT_NAME" && \
+        git config --global user.email "$GIT_EMAIL" && \
         echo "Git configuration complete"; \
     else \
-        echo "Warning: GIT_USER_NAME and GIT_USER_EMAIL not set in .env"; \
-        echo "Git commits will require manual configuration"; \
+        echo "Warning: No git user configured on host system"; \
+        echo "Run 'git config --global user.name "Your Name"' and 'git config --global user.email "you@example.com"' on host first"; \
     fi'
 
 # Set working directory to mounted volume