fix: use log_step (cyan) for progress messages instead of log_warn (yellow) (#534)

~1500 progress messages across 481 files were using log_warn (yellow)
for normal status updates like "Installing...", "Setting up...",
"Creating server...", etc. This made users think something was wrong
when everything was proceeding normally.

Changes:
- Replace log_warn with log_step for all progress/status messages
- Keep log_warn only for actual warnings (errors, remediation hints)
- Remove emoji from 3 sprite completion messages

Agent: ux-engineer

Co-authored-by: A <6723574+louisgv@users.noreply.github.com>

github-codespaces/codex.sh

@@ -38,7 +38,7 @@ CODESPACE_NAME="$CODESPACE"
 wait_for_codespace "$CODESPACE"
 
 # 4. Install codex
-log_warn "Installing codex..."
+log_step "Installing codex..."
 run_server "npm install -g @openai/codex"
 log_info "codex installed"
 
@@ -62,7 +62,7 @@ log_info "Codespace: $CODESPACE"
 echo ""
 
 # 7. Start codex interactively
-log_warn "Starting codex..."
+log_step "Starting codex..."
 log_warn "To delete codespace later, run: gh codespace delete --codespace $CODESPACE --force"
 echo ""
 sleep 1