fix(mrt-utilities): strip development export conditions during pack to prevent consumer resolution failures

[bendvc]

PR Description

Why this change

@salesforce/mrt-utilities exposed development export conditions that point to ./src/*, while the published package only ships dist/*.
In environments that include the development condition (for example Vite dev resolution), consumers can match development first and attempt to load non-published source files, causing module resolution failures instead of falling back to import/require.

What we changed

• Added packages/mrt-utilities/scripts/strip-dev-exports.cjs.
• Added lifecycle hooks in packages/mrt-utilities/package.json:
  • prepack: runs the strip script to remove development keys from exports.
  • postpack: restores package.json via git checkout package.json.
• Added a changeset:
  • .changeset/mrt-utilities-strip-dev-exports.md (@salesforce/mrt-utilities: patch).

Existing pattern reused

This follows the same proven approach already used in @salesforce/b2c-tooling-sdk:

• Keep development export conditions in source for local monorepo/dev ergonomics.
• Remove those conditions during packing/publishing so npm consumers only resolve to published dist artifacts.

Smoke test steps

1. From repo root, run:
   • pnpm --filter @salesforce/mrt-utilities pack --pack-destination /tmp
2. Verify command output includes:
   • prepack execution and Stripped "development" condition from ... export(s)
   • successful tarball creation (e.g. /tmp/salesforce-mrt-utilities-<version>.tgz)
3. Verify packed contents are publish-safe:
   • tarball lists dist/**, package.json, README.md
   • no src/** files in tarball
4. (Optional extra check) inspect packaged package.json inside tarball and confirm exports entries do not include development.
5. Confirm working tree still contains intended source changes after test (if needed, re-open packages/mrt-utilities/package.json to verify prepack/postpack scripts remain present).