fix(ci): align nightly build contracts

[wgqqqqq]

Summary

• exercise Nightly prerelease version projection and locked Cargo metadata in the ordinary three-OS CI matrix
• run Windows ConPTY terminal contracts in regular CI and serialize native PTY tests in CI/Nightly
• restore macOS FSEvents file-watch contracts after repeated local stress validation
• fix the Relay image smoke command's YAML folding and add workflow-shape regression coverage
• strengthen build-version projection coverage so workspace lock entries update while non-workspace dependency versions remain unchanged

Root cause

Regular CI and Nightly validated different working-tree states. Nightly projected package versions before nested cargo --locked hooks, while regular CI only checked committed manifests. Platform-only tests and the Relay publish smoke path were also Nightly-only, allowing a green commit to fail deterministically during packaging.

Verification

• node --test --test-name-pattern='nightly|build version projection' scripts/release-channel.test.mjs scripts/check-github-config.test.mjs
• git diff --check upstream/main...HEAD
• isolated full-workspace version projection followed by cargo metadata --locked --no-deps
• macOS file_watch_contracts: 10 consecutive runs, 9/9 passing each run

The full local GitHub-config test entry point additionally reaches an upstream PowerShell truth-table test; this machine does not have pwsh, so that pre-existing test cannot execute locally. The changed Nightly/release contract tests pass.