fix(agent): describe typed historical comparison charts

Use time_comparison for current curves and historical point sets. Document shared time slots and aligned real sample timestamps; synchronize the generated chart contracts.

docs/agent-ui-protocol.md

@@ -36,6 +36,8 @@ Task display is asynchronous: Server verifies the task/run/generation, active le
 
 Task open_chart requires persisted evidence references. Task set_overlay can omit data; Server resolves immutable evidence into bounded GeoJSON. Supplied data must match that resolution and never overrides the stored snapshot. Chat and Dev supply resolved data for structural validation before rendering.
 
+Same-time-of-day current/history comparisons use `chart_type=time_comparison`; ordinary charts retain `line` or `bar`. The comparison axis contains shared UTC+8 `HH:mm` or `HH:mm:ss` slots, with current `line` and historical `scatter` series and aligned real `sample_times`. The Server automatically validates new task presentation and report chart publications, rejecting date-appended axes, missing timestamps, misplaced points and nonhistorical reference dates with `TIME_COMPARISON_INVALID`. Ordinary charts skip this semantic check. Historical stored chart read contracts remain unchanged.
+
 Chat, task following and Dev previews share the frontend command dispatcher but own independent map sources, SCADA layers and chart state. Clearing or switching one owner does not clear another. Dev JSONL is an explicit local preview/import/export container, not an alternative online business protocol. Plain data records and ui_block records do not execute embedded actions. The earlier agent-ui@1 registry has no active tool mappings and is not an action entry point.
 
 ## Running and waiting input delivery