test: downstream wire-compat (vectors + smoke)

Phase 2 of ether/etherpad#7923. Adds this repo's first test runner
(node:test via tsx) plus two suites:

- test:vectors — server-free, replays the canonical wire-format fixture
  through the repo's own Changeset/AttributePool decoders and asserts
  byte-for-byte text equality. All 5 vectors pass with no decoder changes.
- test:smoke — live HTTP+socket.io round-trip; skips cleanly when no
  server/API key is available.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: JohnMcLear

package.json

@@ -39,13 +39,17 @@
     "@types/superagent": "^8.1.7",
     "eslint": "^9.32.0",
     "eslint-config-etherpad": "^3.0.13",
+    "tsx": "^4.22.4",
     "typescript": "^5.4.2"
   },
   "scripts": {
     "build": "tsc",
     "prepublishOnly": "npm run build",
     "lint": "eslint .",
-    "lint:fix": "eslint --fix ."
+    "lint:fix": "eslint --fix .",
+    "test": "pnpm run test:vectors && pnpm run test:smoke",
+    "test:vectors": "tsx --test test/vectors.test.ts",
+    "test:smoke": "tsx --test test/smoke.test.ts"
   },
   "engines": {
     "node": ">=18.0.0"

pnpm-lock.yaml

@@ -0,0 +1,7 @@
+[
+  {"name":"plain-insert","initialText":"abc\n","changeset":"Z:4>3=3+3$XYZ","pool":{"numToAttrib":{},"nextNum":0},"resultText":"abcXYZ\n"},
+  {"name":"plain-delete","initialText":"abcdef\n","changeset":"Z:7<3=1-3$","pool":{"numToAttrib":{},"nextNum":0},"resultText":"aef\n"},
+  {"name":"formatted-insert","initialText":"abc\n","changeset":"Z:4>4=3*0+4$bold","pool":{"numToAttrib":{"0":["bold","true"]},"nextNum":1},"resultText":"abcbold\n"},
+  {"name":"multiline-insert","initialText":"abc\n","changeset":"Z:4>8=3|2+8$one\ntwo\n","pool":{"numToAttrib":{},"nextNum":0},"resultText":"abcone\ntwo\n\n"},
+  {"name":"attrib-reuse","initialText":"abc\n","changeset":"Z:4>2*0+1=3*0+1$AB","pool":{"numToAttrib":{"0":["bold","true"]},"nextNum":1},"resultText":"AabcB\n"}
+]