refactor(sight): split static_rules.go into static_rules_defaults.go

Move the defaultRules() built-in rule set (~855 lines) verbatim into a
new same-package file static_rules_defaults.go, leaving static_rules.go
with the analyzer logic and helpers. No behavior or API changes.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Patel230