[V2:22] Add Template Workspace Deferment

[ritorhymes]

Part of V2: Multi-repo local build system.

Summary

This PR is the template repo V2 deferment slice: it gives build-eips a tracked repo_id = "template" manifest while intentionally collapsing production and staging to the canonical eips-wg/template repo and GitHub Pages URL until a distinct production target exists, with an inline manifest comment recording why and when to split them. Unlike the EIPs/ERCs rollout PRs, it does not add sibling topology, README workflow docs, or real raw-template workspace bootstrap; the POSIX and PowerShell scripts/dev-setup entries are explicit failing stubs that exit with an error and redirect users to EIPs/ERCs setup, alongside contributor guidance explaining the deferment. It still aligns CI and publish with the final V2 command surface (editorial check --against-upstream --format github as the V2:14 targeted editorial surface, plain build since V2:15 moved eipw out of build/check/serve, plus template-specific step labels), so review should focus on the manifest deferment contract, stub failure guidance, and CI/publish command migration rationale.

• Add .build-eips.repo.toml for the template repo.
• Point both production and staging metadata at the canonical eips-wg/template repository and GitHub Pages URL until a distinct production target exists.
• Include an inline manifest comment recording why production and staging collapse, and when future editors should split them.
• Update CI from check --format github to editorial check --against-upstream --format github.
• Update publish builds from build --no-lint to plain build and remove the old --no-lint justification comment.
• Rename stale EIPs-labeled workflow steps to template-specific build/check labels.
• Add POSIX and PowerShell scripts/dev-setup stubs that fail clearly and direct users to bootstrap from EIPs or ERCs.
• Add contributor guidance explaining that raw template-repo workspace bootstrap is deferred.

Review Notes

This PR intentionally does not mirror the full EIPs/ERCs workspace rollout from V2:20 and V2:21. The template repo is included in the V2 system, but raw template-repo bootstrap is not a supported entrypoint yet.

The repo manifest gives build-eips a stable repo_id = "template" identity for future use. Production and staging intentionally collapse to the same repository and base URL because template does not yet have a separate production deployment target. The inline manifest comment records that deferment directly in the config.

The setup scripts are explicit stubs. They exit with an error instead of pretending that raw template bootstrap is ready, and they direct users to start from the active EIPs or ERCs repo with ./scripts/dev-setup.

The CI and publish changes align this repo with the V2 command surface. editorial check --against-upstream --format github is the validation command, and publish no longer passes --no-lint because V2:15 removes eipw linting from general build/check/serve commands.

Unlike EIPs/ERCs, this PR does not add README local workflow docs, sibling repo declarations, or real workspace bootstrap behavior. Those remain deferred until template has a first-class raw-repo workflow.

Verification

• Review .build-eips.repo.toml for repo_id = "template", the intentional production/staging collapse, and the inline deferment comment.
• Review .github/workflows/ci.yml for the editorial check --against-upstream --format github command and template-specific step label.
• Review .github/workflows/publish.yml for the plain build publish command, removed --no-lint comment, and template-specific step label.
• Review .github/CONTRIBUTING.md for the deferred-bootstrap guidance and EIPs/ERCs handoff.
• Review scripts/dev-setup and scripts/dev-setup.ps1 for explicit failure behavior and consistent guidance.