[design] README Quick Start corrections

[rorygraves]

README Quick Start corrections

Problem

The root README.md has a "🚀 Quick Start" section that looks complete but
misleads a first-time contributor:

• It lists Scala 2.13 in the Quick Start prerequisites and again in
  Architecture → Technology Stack, but the build is Scala 3.7.1
  (build.sbt: ThisBuild / scalaVersion := "3.7.1").
• The rest of the Quick Start (prerequisites, .env setup, backend/frontend
  run steps, ports) is spread across the file and has not been verified to be
  internally consistent and correct against the repo.

Net effect: a new user following the steps top-to-bottom can hit an incorrect
fact and stall before getting a server running.

Approach

A documentation-only revision of README.md. No source, build, or
.env.example changes.

1. Correct the Scala version everywhere it appears. Replace "Scala 2.13"
   with "Scala 3" in both the Quick Start prerequisites and the
   Architecture → Technology Stack section. Plain "Scala 3" is preferred over
   pinning "3.7.1" in prose so the README does not drift on the next bump; the
   exact version stays in build.sbt.

2. Verify and correct the remaining Quick Start facts against the repo, and
   leave correct ones unchanged. Verified during design:

   • Toolchain in use: Java 21 (java -version), sbt 1.11.3
     (project/build.properties). The README's "Java 17+" / "sbt 1.8+" are
     stated as minimums — keep unless shown to be wrong; do not regress them.
   • Node.js prerequisite for the frontend.
   • .env setup: .env.example exists in the repo root; cp .env.example .env
     is correct.
   • Backend start: sbt szorkStart and sbt "~szorkStart".
   • Frontend: cd frontend, npm install, npm run dev; dev server is Vite
     on port 3090 (frontend/vite.config.mts), URL http://localhost:3090.
   • Ports: HTTP 8090 (SzorkConfig.scala) and WebSocket 9002
     (SzorkServer.scala) — already correct in the README.

3. Keep the section tight and linear — a single clone → configure → run
   path, ordered so the steps work in sequence.

Decisions

• The human dismissed the clarifying questions, so defaults were taken:
  • Interpretation: improve the existing README Quick Start, not create a
    new file.
  • Factual accuracy is in scope — the Scala version mismatch is fixed as
    part of this work.
• Version is written as "Scala 3" (not "3.7.1") in prose to avoid future drift;
  build.sbt remains the single source of truth for the exact version.

Scope: single piece

This is one small, internally-consistent edit to a single file, comfortably
reviewable in one sitting. The feature is therefore a single piece (p1).
Splitting it into setup/edit/cleanup stages would add overhead without value.

Non-goals

• No new standalone QUICKSTART.md — the README section is the home for this.
• No rewrite of unrelated README sections (Features, How It Works, About,
  Contributors, License) beyond the version corrections noted above.
• No changes to source code, build files, or .env.example.
• No expansion into troubleshooting, Docker, or deployment docs.

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[chatgpt-codex-connector]

Correct the verified Node prerequisite

This marks the existing frontend Node.js prerequisite as verified, but the checked-in lockfile requires newer Node for the frontend toolchain: frontend/package-lock.json lists vite 7.1.2 and @vitejs/plugin-vue 6.0.1 with engines ^20.19.0 || >=22.12.0. If the README keeps its current Node.js 18+ prerequisite, contributors on Node 18 will fail during npm install/npm run dev, so the design should require updating the Quick Start minimum instead of treating that fact as already correct.

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