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-proof-push/scripts/proof_push.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+# Push a markdown file to a running Proof server and return the document URL.
+# Usage: proof_push.sh <path-to-markdown> [server-url]
+set -euo pipefail
+
+FILE="${1:?Usage: proof_push.sh <markdown-file> [server-url]}"
+SERVER="${2:-http://localhost:4000}"
+UI_URL="${3:-http://localhost:3000}"
+
+if [[ ! -f "$FILE" ]]; then
+  echo "error: file not found: $FILE" >&2
+  exit 1
+fi
+
+TITLE=$(basename "$FILE" .md)
+
+RESPONSE=$(curl -s -X POST "${SERVER}/share/markdown" \
+  -H "Content-Type: application/json" \
+  -d "$(jq -n --arg md "$(cat "$FILE")" --arg title "$TITLE" '{markdown: $md, title: $title}')")
+
+SLUG=$(echo "$RESPONSE" | jq -r '.slug // empty')
+ERROR=$(echo "$RESPONSE" | jq -r '.error // empty')
+
+if [[ -z "$SLUG" ]]; then
+  echo "error: failed to create document${ERROR:+: $ERROR}" >&2
+  echo "$RESPONSE" >&2
+  exit 1
+fi
+
+TOKEN_PATH=$(echo "$RESPONSE" | jq -r '.tokenPath // empty')
+
+echo "slug: $SLUG"
+echo "url: ${UI_URL}/d/${SLUG}"
+[[ -n "$TOKEN_PATH" ]] && echo "editor-url: ${UI_URL}${TOKEN_PATH}"