Remove credibility-based enforcement bypasses

[cmdr-chara]

Summary

• remove follower-count and PageRank/UserCred early exits from baked user and post abuse-enforcement rules
• preserve explicit allowlist and missing-entity guardrails
• preserve the legacy CEL field for dynamic-rule compatibility without using it as a baked credibility bypass
• add focused pipeline tests and document ordered semantics plus GrowthBook synchronization requirements

Why

Credibility and popularity can be evidence inputs, but should not make an account or author categorically immune from otherwise applicable abuse enforcement.

Verification

• Rust source parsed with rustfmt --edition 2024
• focused rule invariant checks
• git diff --check / git show --check

The public abuse-service snapshot omits its Cargo manifest, so the Rust tests cannot be executed here. Production GrowthBook rules must be updated with the same removals or they may continue overriding the baked fallback.