@W-20937015: Adding windows test support

[amit-kumar8-sf]

Summary

Adds Windows CI coverage for the B2C developer tooling monorepo by introducing a sibling test-windows job alongside the existing Linux test job in ci.yml, following the pwa-kit pattern (pwa-kit / pwa-kit-windows).

• New composite action .github/actions/setup-windows/action.yml — Node + pnpm + pnpm-store cache + pnpm install --frozen-lockfile for reuse across all Windows jobs.
• .github/workflows/ci.yml — new test-windows job (matrix: [22.x, 24.x]) running SDK → MCP → CLI → VS Extension checks with Windows-suffixed coverage and test-result artifacts. Includes a diagnostic Print Windows test failures step that parses each package's test-results.json and echoes failing titles + error snippets to the job log (Mocha's JSON reporter otherwise hides the failures behind an opaque non-zero exit code).
• .github/workflows/e2e-tests.yml + .github/workflows/e2e-shell-tests.yml — bash-default shell wiring so existing E2E matrices can be extended to Windows in a follow-up without re-doing shell quirks.
• Test fixes for Windows path/permission assumptions (behavior unchanged on POSIX):
  • packages/b2c-tooling-sdk/test/operations/debug/source-mapping.test.ts — use path.resolve so expectations match the drive-prefixed absolute path production returns on Windows.
  • packages/b2c-tooling-sdk/test/discovery/utils.test.ts — normalize glob results to POSIX slashes before asserting.
  • packages/b2c-tooling-sdk/test/scaffold/registry.test.ts — assert SCAFFOLDS_DATA_DIR via path.join('data', 'scaffolds') so the substring check works on both separators.
  • packages/b2c-dx-mcp/test/tools/mrt/index.test.ts — switch 4 path.join(projectDir, 'build') expectations to path.resolve(...) (matches services.resolveWithProjectDirectory).
  • packages/b2c-dx-mcp/test/services.test.ts — path.resolve(projectDir, 'subdir') assertion.
  • packages/b2c-cli/test/commands/mrt/save-credentials.test.ts — skip the 0o600 mode-bit assertion on win32; NTFS doesn't honor POSIX mode bits, credential files are protected via ACLs.
• Production fixes for real Windows bugs uncovered by the new matrix:
  • packages/b2c-tooling-sdk/src/plugins/loader.ts — convert hook path to a file:// URL via pathToFileURL(hookFilePath).href before dynamic import(). Node's ESM import() on Windows rejects raw backslash/drive-letter paths. Without this fix, every hook-based plugin silently failed to load on Windows.
  • packages/b2c-dx-mcp/src/tools/storefrontnext/site-theming/theming-store.ts — replace filePath.startsWith('/') (POSIX-only absolute detection) with path.isAbsolute() so THEMING_FILES env entries resolve on both platforms; harden emoji-anchored section regexes with explicit Unicode escapes (\u26A0\uFE0F?, \u{1F4CB}, \u{1F504}, \u2705, \u{1F4DD}) and \r?\n CRLF tolerance to be robust against Git line-ending conversion on Windows checkouts.
• packages/b2c-cli/package.json — new sibling script test:ci:win that runs the same Mocha suite with c8 --check-coverage=false. Used only by the Windows CI step; Linux test:ci is untouched and continues to enforce the 70% function-coverage gate.

Design notes:

• Sibling job (not an os matrix row) — keeps the existing Ubuntu job untouched, allows an independent Windows Node matrix, and produces clearly labelled Windows reports/artifacts.
• All Windows jobs use defaults.run.shell: bash so the existing env VAR=value mocha … inline-env npm scripts keep working unchanged under Git Bash — no cross-env dependency or script rewrites required.
• ${{ runner.os }} produces a distinct Windows-pnpm-store-* cache key, preventing cross-OS cache pollution.
• Advisory rollout: test-windows is marked continue-on-error: true. Windows coverage is new and the last infrastructure-level quirk (V8 coverage on Windows double-counting some TS files via the tsx loader registering them under two URL casings, dragging CLI function coverage from ~78% down to ~68%) is surfaced but not gated. The per-matrix test-results-windows-node-* artifact is always uploaded and the diagnostic Print Windows test failures step renders failures inline, so any remaining platform-specific issue can be read directly from the Actions run. Each job has a comment flagging that continue-on-error should be removed once Windows tests are consistently green.

Testing

Infrastructure + cross-platform test-hardening change; verified as follows:

• YAML parses cleanly on all edited workflow files.
• Scoped unit-test runs on POSIX (macOS) after every change:
  • b2c-tooling-sdk operations/debug, plugins, scaffold, discovery — 209 passing.
  • b2c-dx-mcp mrt + site-theming — 149 passing.
  • b2c-cli mrt — 13 passing.
• c8 --check-coverage=false confirmed locally to disable the threshold gate while still producing coverage/lcov.info for artifact upload.
• No new linter errors on any touched file (pnpm run lint in each affected package).
• End-to-end validation of the new Windows matrix happens on the first PR run (test-windows at [22.x, 24.x]). The previous 24-failure baseline from the last Windows run is now expected to drop to 0 blocking failures with this PR.

Dependencies

• No net-new third-party dependencies were added
• If net-new third-party dependencies were added, rationale/discussion is included and 3pl-approved is set by a maintainer

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• Tests pass (pnpm test) — all scoped suites pass locally on macOS; Windows matrix runs with continue-on-error: true during the advisory rollout
• Code is formatted (pnpm run format) — ran lint on every modified file, no linter errors

[clavery]

Looks pretty good. I like that we're skipping errors for now. Will test the loader.ts change