[codex] Recalibrate CII severity and salience scoring (#3927)

* feat(cii): recalibrate bias-sensitive scoring

* fix(cii): address greptile feedback on v3 recalibration

- docs/methodology/cii-risk-scores.mdx: correct 500K anchor from +9 to
  +10 in the displacement-boost migration note. Math.round((log10(500000)
  - 5) * 8 + 4) = Math.round(9.59) = 10. Clients re-baselining on this
  note would otherwise build a one-point-low expectation around the
  500K-displaced threshold (greptile P2).

- server/worldmonitor/intelligence/v1/get-risk-scores.ts: mirror the
  same fix in the inline comment at the formula site (greptile P2,
  out-of-diff).

- src/services/country-instability.ts: drop the dead `adjustedCount`
  alias in calcInformationScore. It was a residual from the previous
  formula where the value was multiplied by eventMultiplier; the
  multiplier was removed in this PR but the alias was left behind
  (greptile P2). baseScore now reads `Math.min(40, count * 5)` directly.