fix: portability — config quoting, configurable base branch, cross-platform date

Summary

Three portability fixes so the skills run cleanly outside the original macOS + dev-branch setup.

Fixes

• config.env.example — quote DEV_ROLE / REVIEW_ROLE; values with spaces broke source .claude/config.env (command not found: React).
• push.md + create-branch.md — use $PROJECT_BASE_BRANCH (fallback dev) instead of a hardcoded dev branch in the protected-branch guard, checkout/pull, and output.
• logwork.md + daily-report.md — add a GNU date -d 'yesterday' fallback for the yesterday arg, which previously only worked on macOS (date -v).

Test plan

• source .claude/config.env on a config with spaced roles → no error
• /create-branch + /push on a repo whose base is master/develop
• /logwork yesterday / /daily-report yesterday on Linux