Update test-examples.sx to reference the real path-derived names
(~geography/<domain>/<stem>) instead of short aliases, drop the
alias chains in run_tests.ml, and add marshes/_islands loading so
the migrated one-per-file islands resolve. Fix the try-rerender-page
stub in boot-helpers.sx to accept the 3 args its callers pass.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>