fix(compaction): keep standing output tokens whole across goal caps

[TheGreatAxios]

Summary

• Caps the live spine goal and the 500-character file goal without splitting standing KEY=value tokens
• Strips the spine cut sentinel when parsing a prior Goal line so a without-file fold does not insert ... into artifact.goal
• Keeps a spaceless 160-character prefix on the Goal line instead of rendering Goal: ... only

Verification

• bun run check passes (7847 tests, 0 fail)

Fixes CL-9501

[linear-code]

CL-9501