fix: restore control system display name events

[stakach]

ControlSystem display_name changes now notify running services again. Remove only display_name from this model's ignored columns; remaining ControlSystem exclusions and Zone's separate policy are unchanged.

Review and verification

• Regression uses ordinary saves to set and clear display_name alongside ignored description changes, checking persistence, CDC rows and PostgreSQL notifications.
• Red: 6 specs, one failure proving the expected update row was suppressed before this change.
• Remaining metadata/telemetry suppression and runtime update controls retained.
• README documents explicit replacement of the installed ten-column policy with the corrected nine-column policy, plus earlier-policy alternatives.
• Independent source/spec/docs review approved. Formatting and Ameba pass (181 files).
• Focused green: 6 specs, zero failures/errors. Full stable/unstable CI and all PR/style checks passed at e82e54f: https://github.com/PlaceOS/models/actions/runs/35052217743.

Completes the user correction tracked in PlaceOS/local#146.