Fix: render drain/drain_prepare/drain_publish swimlane phases

[ChaoWao]

Summary

#1304 added the sync_start stop-the-world drain phase kinds — Drain,
DrainPrepare, DrainPublish — to both the device emit
(l2_swimlane_profiling.h) and the host serializer
(l2_swimlane_collector.cpp, which maps them to "drain" /
"drain_prepare" / "drain_publish"), but never taught the Python
renderer about them.

swimlane_converter.py drops any phase outside its sched-lane whitelist.
A sync_start SPMD cohort launches through handle_drain_mode →
drain_stage_cores, so its actual launch is emitted as drain_publish,
not dispatch. Result: the drain records were produced on-device and
written to l2_swimlane_records.json, but silently filtered out at
render time — the scheduler dispatch work for every sync_start cohort
vanished from the Perfetto trace.

This wires the three phases into the renderer:

• Add drain / drain_prepare / drain_publish to phase_colors
  (cq_build color family; the outer drain bar time-contains the two
  inner staging passes, so Perfetto nests them by depth on the track).
• Add the three phases to the sched-lane render whitelist.

Testing

Verified on a2a3 silicon at l2_swimlane_level=4 — for each workload the
rendered scheduler-lane phase histogram now matches the raw record kinds:

workload	drain	drain_prepare	drain_publish
spmd_sync_start	3	2	2
spmd_sync_start_early_dispatch	3	3	3
spmd_sync_start_stress	36	24	24

qwen3_14b_decode (no sync_start) is unaffected — dispatch/complete
render as before.

• Hardware tests pass (a2a3, level-4 swimlane, four workloads)
• Simulation tests (renderer-only Python change; not arch-specific)

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: ca9862ae-a82b-4d6a-8df4-eb23dacc3ed4

📥 Commits

Reviewing files that changed from the base of the PR and between cb75bec and c3ed783.

📒 Files selected for processing (1)

• simpler_setup/tools/swimlane_converter.py

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📝 Walkthrough

Walkthrough

Scheduler phase visualization now recognizes drain, drain_prepare, and drain_publish, assigning each a Perfetto color and allowing them through trace rendering.

Changes

Scheduler drain phases

Layer / File(s)	Summary
Recognize and color drain phases simpler_setup/tools/swimlane_converter.py	Adds colors for the three drain phases and includes them in the Scheduler’s allowed-phase filter.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Poem

I’m a rabbit with traces hopping bright,
Drain phases now bloom in colored light.
Prepare and publish join the run,
No unknown phase is skipped or shunned.
Three little names make swimlanes fun!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: rendering the new drain-related swimlane phases.
Description check	✅ Passed	The description is directly related to the code change and accurately explains the renderer updates and motivation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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