fix(csharp): add NuGet badges to GitHub release body

[konard]

Summary

Closes follow-up on #88 — "Still no NuGet badges in C# GitHub releases."

The C# release script (csharp/scripts/create-github-release.mjs) used to write the changelog notes straight into the GitHub release body with no badges, while the Rust release script already injected Crates.io + Docs.rs shields.io badges that link to the specific package version. As a result, every C# release page (e.g. csharp-v2.4.0) was missing the NuGet version + downloads badges that the Rust release pages have.

This PR mirrors the Rust pattern for C#:

• buildNugetBadges(packageId, version) emits [![NuGet](…/nuget/v/<id>)](nuget.org/packages/<id>/<version>) [![NuGet Downloads](…/nuget/dt/<id>)](nuget.org/packages/<id>/<version>).
• prependNugetBadges(notes, packageId, version) injects the badges above the changelog/Package footer and is a no-op when the badges are already present or --package-id is omitted.
• buildReleasePayload(...) wires the badge logic into the release API payload so that every future C# release published by CI carries the badges.
• Refactored the script for testability (gated CLI execution behind isCliEntryPoint()) so the helpers can be unit-tested.

The existing csharp-v2.4.0 release body was backfilled via gh release edit so the fix is visible immediately, not only on the next release. See docs/case-studies/issue-88/github-data/csharp-v2.4.0-release-after-fix.json for the post-fix snapshot.

Template comparison

The upstream csharp-ai-driven-development-pipeline-template/create-github-release.mjs already implements buildNuGetBadge and appendNuGetBadgeIfMissing — link-cli had drifted from it. Snapshot kept under docs/case-studies/issue-88/templates/ for evidence. Nothing to report upstream.

Test plan

• node --test csharp/scripts/release-scripts.test.mjs — 22/22 pass (16 prior + 6 new badge tests).
• --dry-run payload contains both img.shields.io/nuget/v/clink and img.shields.io/nuget/dt/clink linking to nuget.org/packages/clink/<version>.
• prependNugetBadges skips when badges already present (idempotent re-run safe).
• prependNugetBadges is a no-op when --package-id is empty (CLI usability preserved).
• Backfilled csharp-v2.4.0 release body verified on github.com.

Fixes #88

[konard]

Working session summary

PR 90 finalized: #90

• Title updated, draft cleared, ready for review.
• 2 commits pushed: fix(csharp): add NuGet badges to GitHub release body + docs(case-study): document NuGet badge follow-up.
• .gitkeep placeholder removed.
• All CI checks green (Lint, Tests on macOS/Ubuntu/Windows, Build Package).
• 22/22 unit tests pass; csharp-v2.4.0 release body already backfilled with NuGet badges.

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This summary was automatically extracted from the AI working session output.

[konard]

🤖 Solution Draft Log

This log file contains the complete execution trace of the AI solution draft process.

💰 Cost: $5.067205

📊 Context and tokens usage:

Claude Opus 4.7: (2 sub-sessions)

1. 114.3K / 1M (11%) input tokens, 27.0K / 128K (21%) output tokens
2. 42.5K / 1M (4%) input tokens, 3.8K / 128K (3%) output tokens

Total: (10.7K new + 144.5K cache writes + 6.4M cache reads) input tokens, 37.3K output tokens, $5.067205 cost

🤖 Models used:

• Tool: Anthropic Claude Code
• Requested: opus
• Model: Claude Opus 4.7 (claude-opus-4-7)

📎 Log file uploaded as Gist (2339KB)

• View complete solution draft log

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Now working session is ended, feel free to review and add any feedback on the solution draft.

[konard]

🎉 Auto-merged

This pull request has been automatically merged by hive-mind.

• All CI checks have passed

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Auto-merged by hive-mind with --auto-merge flag