ci: prevent tag-dispatch dry runs from publishing NuGet packages

[AGiorgetti]

A manual dispatch on a tag with dry_run=true could reach the production NuGet publish job even when publish=false. Require a push event for automatic tag publishing; retain explicit manual publishing on main/release//hotfix/ with publish=true, dry_run=false, successful artifact prerequisites, and production approval.

Fixes #19.

Changes

• One production condition line changed; package validation, provenance/checksums, environment protection, and publishing commands are preserved.
• Add 154 MSTest cases evaluating actual workflow expressions and dependencies: the 96 event/ref/input cases, 48 failed/cancelled/skipped prerequisite cases, tag rehearsals, authorized stable/prerelease tag pushes and manual branch publishing, unsupported events, and absent inputs.
• Execute the extracted publishing script only with local dotnet mocking and a fake key. Dry runs must schedule no publish job and record zero pushes.
• Synchronize release checklist, changelog, and issue-specific control-document evidence.

Validation

• Test-first baseline on unchanged YAML: 20 failed, 134 passed, zero skipped. Both tag rehearsals recorded three mocked push calls, including publish=false; non-dry-run tag dispatches already skipped pack despite the unsafe raw publish expression.
• Fixed focused suite: 173/173 passed, zero skipped (154 new + 19 existing release-quality cases).
• Release solution build: zero warnings/errors. YAML parsing and CRLF-aware whitespace checks pass.
• Full solution run: 806 passed, 2 failed due to stale sample NuGet assets (NETSDK1064), 1 Native AOT prerequisite skip. Regenerating assets and rebuilding recovered both failures; affected tests plus release regressions then passed 175/175, zero skipped. All 808 executed cases have passing evidence across the full run and targeted recovery, not a single all-green full-suite invocation.
• Independent read-only review accepted the change and coverage. Exact-head ordinary PR CI passed; detailed results follow.

Exact-head CI

CI run 37113397730 completed successfully for pull_request on 34d0549132b50bf0c0e09dd6e143ea1d26f7ea66.

• Both Windows and Linux full suites: 809 passed per platform, zero failures/skips (568 generator, 235 packaging, 5 runtime, 1 integration). This includes all new publishing regressions and required trimming/Native AOT validation.
• All six Roslyn host jobs passed (4.8.0, 4.14.0, 5.9.0 on both platforms).
• Pack & Validate, Verify Release Artifacts, and Publish NuGet Packages were all skipped.
• Remote branch, PR head, and CI head match. PR remains draft against develop; working tree is clean.

Limits

The local evaluator covers the current Actions expression subset and dependency graph, not live production approval behavior. Local Native AOT is inconclusive because the MSVC C++ linker toolchain is absent. No release workflow was dispatched, no real NuGet push ran, and no tags, security settings, or merges were changed. AgentStack CLI layout incompatibility required the repository-authorized GitHub CLI fallback.

Prepared with OpenAI Codex.

[AGiorgetti]

The changelog is wrong! the fix should be listed in a "## Fixes" section in a new "## Unreleased" section (top of the file) instead of updating an already existing release