Fix Deno display_data to use broadcast API

[rgbkrk]

Summary

The previous PR showed that Deno.jupyter.html tagged template doesn't emit display_data messages (test showed ⏭️ skipped), but Deno.jupyter.broadcast("display_data", ...) does work (update_display_data test passed ✅).

This PR:

• Changes Deno display_data_code to use Deno.jupyter.broadcast("display_data", ...)
• Clarifies that evcxr requires trait implementation for display_data

Expected Results

• Deno display_data: ⏭️ → ✅
• Deno should go from 19/24 to 20/24

[github-actions]

Kernel Conformance Matrix

Kernel	Tier 1	Tier 2	Tier 3	Tier 4	Total
deno	8/9	6/7	3/3	3/5	20/24
evcxr	9/9	3/7	1/3	3/5	16/24
ipykernel	9/9	7/7	3/3	5/5	24/24

---

deno (Deno kernel) - 3 failures, 1 skipped

Language: typescript | Protocol: 5.3

Failures

Test	Message Type	Likely Source	Reason
interrupt_request	interrupt_request	unknown	Timeout waiting for control reply
shutdown_reply	shutdown_request	unknown	Timeout waiting for control reply

Skipped (Not Implemented)

• stdin_input_request: Kernel can request input from frontend via stdin channel

evcxr (evcxr_jupyter) - 5 failures, 3 skipped

Language: Rust | Protocol: 5.3

Failures

Test	Message Type	Likely Source	Reason
inspect_request	inspect_request	unknown	Timeout waiting for shell reply
history_request	history_request	unknown	Timeout waiting for shell reply
comm_info_request	comm_info_request	unknown	Timeout waiting for shell reply
interrupt_request	interrupt_request	unknown	Protocol error: Error deserializing content for msg_type interrupt_reply: missing field status

Skipped (Not Implemented)

• display_data: Kernel can produce display_data messages for rich output
• update_display_data: Kernel can update existing displays via update_display_data
• stdin_input_request: Kernel can request input from frontend via stdin channel

---

Test Results by Message Type

Test	Message Type	deno	evcxr	ipykernel
comm_info_request	comm_info_request	✅	❌	✅
comms_lifecycle	comm_open	✅	✅	✅
complete_request	complete_request	✅	✅	✅
display_data	display_data	✅	⏭️	✅
error_handling	execute_request	✅	✅	✅
execute_input_broadcast	execute_input	✅	✅	✅
execute_reply_ok	execute_request	✅	✅	✅
execute_result	execute_result	✅	✅	✅
execute_stdout	execute_request	✅	✅	✅
execution_count_increments	execute_request	✅	✅	✅
heartbeat_responds	heartbeat	✅	✅	✅
history_request	history_request	✅	❌	✅
inspect_request	inspect_request	✅	❌	✅
interrupt_request	interrupt_request	❌	❌	✅
is_complete_complete	is_complete_request	✅	✅	✅
is_complete_incomplete	is_complete_request	⚠️	⚠️	✅
kernel_info_has_language_info	kernel_info_request	✅	✅	✅
kernel_info_has_protocol_version	kernel_info_request	✅	✅	✅
kernel_info_reply_valid	kernel_info_request	✅	✅	✅
parent_header_correlation	parent_header	✅	✅	✅
shutdown_reply	shutdown_request	❌	✅	✅
status_busy_idle_lifecycle	status	✅	✅	✅
stdin_input_request	input_request	⏭️	⏭️	✅
update_display_data	update_display_data	✅	⏭️	✅

[github-actions]

Kernel Conformance Matrix

Kernel	Tier 1	Tier 2	Tier 3	Tier 4	Total
deno	9/10	6/7	3/3	3/5	21/25
evcxr	10/10	3/7	1/3	3/5	17/25
ipykernel	10/10	7/7	3/3	5/5	25/25

---

deno (Deno kernel) - 3 failures, 1 skipped

Language: typescript | Protocol: 5.3

Failures

Test	Message Type	Likely Source	Reason
interrupt_request	interrupt_request	unknown	Timeout waiting for control reply
shutdown_reply	shutdown_request	unknown	Timeout waiting for control reply

Skipped (Not Implemented)

• stdin_input_request: Kernel can request input from frontend via stdin channel

evcxr (evcxr_jupyter) - 5 failures, 3 skipped

Language: Rust | Protocol: 5.3

Failures

Test	Message Type	Likely Source	Reason
inspect_request	inspect_request	unknown	Timeout waiting for shell reply
history_request	history_request	unknown	Timeout waiting for shell reply
comm_info_request	comm_info_request	unknown	Timeout waiting for shell reply
interrupt_request	interrupt_request	unknown	Protocol error: Error deserializing content for msg_type interrupt_reply: missing field status

Skipped (Not Implemented)

• display_data: Kernel can produce display_data messages for rich output
• update_display_data: Kernel can update existing displays via update_display_data
• stdin_input_request: Kernel can request input from frontend via stdin channel

---

Test Results by Message Type

Test	Message Type	deno	evcxr	ipykernel
comm_info_request	comm_info_request	✅	❌	✅
comms_lifecycle	comm_open	✅	✅	✅
complete_request	complete_request	✅	✅	✅
display_data	display_data	✅	⏭️	✅
error_handling	execute_request	✅	✅	✅
execute_input_broadcast	execute_input	✅	✅	✅
execute_reply_ok	execute_request	✅	✅	✅
execute_result	execute_result	✅	✅	✅
execute_stderr	stream	✅	✅	✅
execute_stdout	execute_request	✅	✅	✅
execution_count_increments	execute_request	✅	✅	✅
heartbeat_responds	heartbeat	✅	✅	✅
history_request	history_request	✅	❌	✅
inspect_request	inspect_request	✅	❌	✅
interrupt_request	interrupt_request	❌	❌	✅
is_complete_complete	is_complete_request	✅	✅	✅
is_complete_incomplete	is_complete_request	⚠️	⚠️	✅
kernel_info_has_language_info	kernel_info_request	✅	✅	✅
kernel_info_has_protocol_version	kernel_info_request	✅	✅	✅
kernel_info_reply_valid	kernel_info_request	✅	✅	✅
parent_header_correlation	parent_header	✅	✅	✅
shutdown_reply	shutdown_request	❌	✅	✅
status_busy_idle_lifecycle	status	✅	✅	✅
stdin_input_request	input_request	⏭️	⏭️	✅
update_display_data	update_display_data	✅	⏭️	✅