docs: reframe README around template usage and fix the stale Test badge

[devantler]

🤖 Generated by the Daily AI Assistant

Fixes #169. Part of the roadmap epic #167 (direction 2 — accurate, helpful docs). Mirrors the merged go-template README enrichment so the two templates read consistently.

Problem

The README didn't read like the front door of a template repository:

• Wrong adoption framing — "Getting Started" told readers to dotnet add package <package-name> from NuGet, and "Usage" was generic dotnet new/dotnet sln boilerplate. This repo is a GitHub template (is_template: true) — the real entry point is Use this template, then renaming Example.
• Broken badge — the Test badge pointed at …/actions/workflows/test.yaml, but there is no test.yaml (workflows are ci.yaml, publish.yaml, release.yaml, sync-labels.yaml, todos.yaml), so it rendered a "not found" status.
• Undocumented value — the README never mentioned the house defaults, the validation/CI model, the release/publish flow, or the AI-maintenance setup.

Change

• Rewrote Getting Started → "Use this template" around the template-usage flow (gh repo create --template / the Use this template button → rename Example → dotnet build/dotnet test).
• Removed the stale Test badge. ci.yaml only runs on pull_request/merge_group (not push: main), so a workflow badge wouldn't render a meaningful status on the default branch, and there's no published NuGet package or .NET-template badge analogous to go-template's Go-ecosystem badges. Kept the accurate License badge. (Acceptance criterion: Test badge fixed or removed.)
• Added a "✨ What's included" section grounded in the actual repo: house defaults (Nullable, ImplicitUsings, AnalysisMode=All, EnforceCodeStyleInBuild, XML docs, TreatWarningsAsErrors), the required-checks CI model + org-required reusable validation workflow, the semantic-release → v* tag → publish-dotnet-library (NuGet) flow, Dependabot/Renovate, and AGENTS.md + .claude/skills/maintain.
• Target framework deferred to the project file (currently net10.0) rather than hardcoded prose, mirroring go-template deferring the Go version to go.mod.

Acceptance criteria

• ✅ README describes a template repo (no "install from NuGet" adoption framing).
• ✅ No broken badges (stale Test badge removed; License badge accurate).
• ✅ A new adopter can tell, from the README alone, what the scaffold provides and how to start.

Validation

Docs-only; every relative link resolves against the repo tree (Example.slnx, src/Example, tests/Example.Tests, .editorconfig, the three workflow files, AGENTS.md). All facts (house-default properties, workflow triggers, release/publish chain) verified against src/Example/Example.csproj, the workflow YAML, .releaserc, and the main branch ruleset.

[github-code-quality]

Code Coverage Overview

Languages: C#

C# / code-coverage/dotnet

The overall coverage in the claude/dotnet-readme... branch is 100%. Coverage data for the main branch is not yet available.

Show a code coverage summary of the most covered files.

File	main	claude/dotnet-readme... 9852a35	+/-
/home/runner/wo...ExampleClass.cs	—	100%	—

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[Copilot]

Pull request overview

Docs-only refresh of the README to reframe it as a template-repository front door rather than a NuGet package, remove the stale Test badge that pointed to a non-existent workflow, and surface what the scaffold actually ships (house defaults, CI, release/publish flow, agent tooling).

Changes:

• Replace "install from NuGet" framing with a "Use this template" flow (gh CLI / Use-this-template button → rename Example → dotnet build/dotnet test).
• Remove the broken Test badge (pointed to a non-existent test.yaml); keep the accurate License badge.
• Add a "✨ What's included" section describing house defaults, CI model, release/publish chain, dependency tooling, and agent setup.

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