Merge step (c): converge to ce-* convention for agents and skills

Aligns local custom agents, skills, and modified shared agents with upstream's
flat ce-<name>.agent.md + ce-<skill>/ convention introduced in upstream v3.x.

Changes:
- Delete 9 upstream-renamed agents for locally-dropped agents (design/*, rails
  reviewers, ankane-readme-writer, data-migration-expert, performance-oracle,
  security-sentinel)
- Delete ce-dhh-rails-style skill (local dropped dhh-rails-style entirely)
- Move 5 custom agents to flat ce-<name>.agent.md paths:
  * python-package-readme-writer, design-conformance-reviewer,
    tiangolo-fastapi-reviewer, zip-agent-validator, lint
- Rename 12 custom skill directories with ce- prefix:
  * john-voice, jira-ticket-writer, hugo-blog-publisher, weekly-shipped,
    proof-push, ship-it, story-lens, sync-confluence, excalidraw-png-export,
    python-package-writer, fastapi-style, upstream-merge
- Port local Python/FastAPI edits into upstream's flat ce-best-practices-
  researcher.agent.md and ce-kieran-python-reviewer.agent.md
- Update frontmatter name: fields in all 17 renamed files to match new paths

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

plugins/compound-engineering/skills/ce-excalidraw-png-export/scripts/setup.sh

@@ -0,0 +1,37 @@
+#!/bin/bash
+# First-time setup for excalidraw-png-export skill.
+# Installs playwright and chromium headless into a dedicated directory.
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+EXPORT_DIR="$SCRIPT_DIR/.export-runtime"
+
+if [ -d "$EXPORT_DIR/node_modules/playwright" ]; then
+  echo "Runtime already installed at $EXPORT_DIR"
+  exit 0
+fi
+
+echo "Installing excalidraw-png-export runtime..."
+mkdir -p "$EXPORT_DIR"
+cd "$EXPORT_DIR"
+
+# Initialize package.json with ESM support
+cat > package.json << 'PACKAGEEOF'
+{
+  "name": "excalidraw-export-runtime",
+  "version": "1.0.0",
+  "type": "module",
+  "private": true
+}
+PACKAGEEOF
+
+npm install playwright 2>&1
+npx playwright install chromium 2>&1
+
+# canvas provides accurate text measurement for convert.mjs.
+# Requires Cairo native library: brew install pkg-config cairo pango libpng jpeg giflib librsvg
+# Falls back to heuristic sizing if unavailable.
+npm install canvas 2>&1 || echo "WARN: canvas install failed (missing Cairo?). Heuristic text sizing will be used."
+
+echo "Setup complete. Runtime installed at $EXPORT_DIR"