feat(globaltool)!: PR-B — thin shims + local tool manifest + workflow regen (#203)

[ChrisonSimtian]

Summary

Second of three PRs from #203. PR-A (#201) shipped the in-tool runner; this PR cuts THIS repo over to thin shims, regenerates the workflows, and updates the framework so downstream consumers re-generating with v11+ get the new shape.

Breaking change: [GitHubActions] generator now emits 3 steps (setup-dotnet + tool restore + dotnet fallout) instead of one ./{BuildCmdPath} {targets} line. Downstream consumers need a .config/dotnet-tools.json with Fallout.GlobalTool pinned for their next workflow regen to be runnable in CI.

This repo's cutover

• .config/dotnet-tools.json — pins Fallout.GlobalTool 10.3.37 (the version just published from feat(globaltool): add in-tool build runner (PR-A of bootstrapper deprecation) #201's merge).
• build.sh / build.ps1 — thin (~60 lines each): kept the dotnet provisioning block verbatim, dropped the BUILD_PROJECT_FILE config + explicit dotnet build/dotnet run --project lines, end with tool restore + dotnet fallout "$@".
• build.cmd — deleted (was a one-line dispatcher to build.ps1).
• .github/workflows/{ubuntu,windows,macos}-latest.yml — regenerated to the new 3-step shape.
• .github/workflows/release.yml — hand-written (kept that way per its header comment); updated to the same shape with the existing NuGetApiKey / GITHUB_TOKEN env mapping preserved.

Framework changes

• Fallout.Common/CI/GitHubActions/Configuration/GitHubActionsRunStep.cs — rewritten to emit 3 steps; drops the BuildCmdPath field.
• Fallout.Common/CI/GitHubActions/GitHubActionsAttribute.cs — stops passing BuildCmdPath to the run step.
• Fallout.Build/CICD/ConfigurationAttributeBase.cs — softens BuildCmdPath to fall back to "build.cmd" instead of asserting when no file is found. Keeps the legacy CI providers (AzurePipelines, AppVeyor, TeamCity, SpaceAutomation) functional for consumers who still have build.cmd, without forcing this repo to keep one. Those providers are dormant / dead-code per Multi-provider CI revival — gather demand for Azure / GitLab / TeamCity / AppVeyor support #8.
• Fallout.Build/Utilities/SchemaUtility.cs — injects a synthetic BuildProjectFile (optional string, with description) into the FalloutBuild base schema. Editors now offer IntelliSense for the BuildProjectFile field that BuildProjectResolver reads from .fallout/parameters.json.
• Fallout.GlobalTool/Program.Setup.cs (WriteBuildScripts) — drops build.cmd emission, emits the thin templates, creates .config/dotnet-tools.json (skipped if one already exists — consumer may have other tools pinned). Drops the now-unused BuildDirectory / BuildProjectName token substitutions in shim templates.
• New template Fallout.GlobalTool/templates/dotnet-tools.json with _FALLOUT_GLOBAL_TOOL_VERSION_ filled at :setup time from the running tool's own assembly version.

Test updates

• SchemaUtilityTest.Test*.verified.json (×4) — add BuildProjectFile after Verbosity.
• CompletionUtilityTest.TestGetCompletionItems{Target,Parameter}Build.verified.txt — add BuildProjectFile: [] in alphabetical position.
• ConfigurationGenerationTest.Test_testName={simple,detailed}-triggers_attribute=GitHubActionsAttribute.verified.txt — expect the new 3-step shape.
• .fallout/build.schema.json — regenerated by the build's own HandleShellCompletionAttribute.

Verification

Locally on Windows:

• dotnet test tests/Fallout.Build.Tests/ — 23/23 passed (schema + completion utility tests).
• dotnet test tests/Fallout.Common.Tests/ --filter ConfigurationGenerationTest — 6/6 passed.
• dotnet test tests/Fallout.GlobalTool.Tests/ — 17/17 passed.
• End-to-end thin-shim cycle: dotnet tool restore resolved Fallout.GlobalTool 10.3.37 from nuget.org, dotnet fallout dispatched into the in-tool runner, which built + ran _build.csproj with the new framework code.

Backwards compatibility

Scenario	Behaviour
Existing consumer repo with old fat build.sh / build.ps1, no v11 changes	Works unchanged. Their shims do their own dotnet build + dotnet run --project; the global tool isn't on their critical path.
Existing consumer repo upgrading to Fallout.GlobalTool v11 and running fallout :setup	:setup overwrites their build.sh / build.ps1 with thin shims, drops build.cmd, and (if they don't already have one) creates .config/dotnet-tools.json. They commit those changes.
Existing consumer repo that regens [GitHubActions] workflows	Workflows now emit the 3-step shape. They need .config/dotnet-tools.json for CI to pass. If they re-run :setup first, it's created automatically; otherwise they add it manually.
Consumer who uses other CI providers (AzurePipelines, AppVeyor, TeamCity, SpaceAutomation)	Unchanged. Those generators still emit ./build.cmd-style invocations and still need build.cmd in the consumer's repo.
Consumer who already has a .config/dotnet-tools.json with other tools pinned	:setup does NOT overwrite. They need to add the fallout.globaltool entry manually (or run dotnet tool install Fallout.GlobalTool from their repo root, which merges into the existing manifest).

Not in scope (follow-up)

• Program.cs Build() method left alive (one bootstrap caller in Program.Complete.cs); shim hop is now redundant but harmless. Cleanup tracked separately.
• Docs sweep tracked in Docs CLI cleanup: replace stale nuke references with fallout across docs/ #198 (PR-C).
• Fallout.Common.targets could surface .config/dotnet-tools.json in the IDE "boot" link group alongside build.sh/build.ps1. Cosmetic; deferred.

Test plan

• ubuntu-latest (the only PR gate) goes green — exercises the new 3-step workflow shape end-to-end (setup-dotnet → tool restore resolves Fallout.GlobalTool 10.3.37 from nuget.org → dotnet fallout Test Pack round-trips through the in-tool runner).
• Post-merge, watch windows-latest and macos-latest runs on main — they exercise the same shape on the other two platforms.
• Post-merge, the release pipeline pushes a new Fallout.GlobalTool version with PR-B's framework changes. PR-C (docs sweep, Docs CLI cleanup: replace stale nuke references with fallout across docs/ #198) can land any time after.

Refs

• This PR: PR-B of the bootstrapper-deprecation plan in Deprecate per-repo bootstrappers; make Fallout.GlobalTool the canonical entry point #203.
• Previous: PR-A (feat(globaltool): add in-tool build runner (PR-A of bootstrapper deprecation) #201) — in-tool runner.
• Next: PR-C (Docs CLI cleanup: replace stale nuke references with fallout across docs/ #198) — docs sweep.