Preserve campaign context between crew and play pages.

Pushed ed59c84.

Fix shipped

When jumping between play.php and crew.php, we now preserve:

• campaign mode flag
• street_cred value
• role picks

That keeps progression state coherent while iterating on crew composition.

Verification

• php tests/run-tests.php -> 53 passed
• Smoke checks confirm campaign/manual and cred params are present in both navigation directions.