Fix pr-creator agent inconsistencies with CLAUDE.md #183

The pr-creator agent has three inconsistencies introduced in #182:

1. Mojibake -- Unicode em dashes corrupted to — in pr-creator.md, needs ASCII -- for terminal/editor robustness.
2. Policy drift -- CI skip guidance for "non-code changes" conflicts with CLAUDE.md requirement that every PR must pass all 4 CI gates.
3. Missing rule -- The no-byline convention (no Co-Authored-By, no "Generated with" footers) exists only in pr-creator.md but not in CLAUDE.md, which is the project source of truth.