Unify product version at 1.4.0, add ruff gate, drop stale GitHub workflow

- One version (1.4.0) across extension/manifest.json, automation/pyproject.toml,
  automation-js/package.json (+lockfile); README documents the bump-together policy
- Delete .github/workflows/ci.yml (behind the Gitea copy; CI runs on Gitea Actions)
- CURSOR_PROMPT.md: replace personal paths with <path-to-context-extractor>
- Add ruff (E4,E7,E9,F,I, line-length 120) to automation/ dev extras, Makefile lint,
  and the Gitea CI Lint + tests job as a hard gate

extension/manifest.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "Context Extractor",
-  "version": "1.3.2",
+  "version": "1.4.0",
   "description": "Extract clean, AI-ready context from any webpage — page content, console logs, network requests, and JS errors. Works unpacked in Chrome and Brave.",
   "permissions": ["activeTab", "scripting", "storage"],
   "host_permissions": ["<all_urls>"],