[Zephyr] Send task stats from Zephyr to Iris

[wmoss]

Describe what changed and why. Follow with bullets for
specific changes if needed. Keep it concise — this text becomes the squash-merge
commit message, so avoid markdown formatting (headers, tables, images).

e.g.

Title: [RL] Fix loss: use global token normalization instead of per-example

"""
This fixes a regression in the DAPO loss computation by switching
from per-example normalization (/ n_i) back to global token
normalization (/ N). Per-example normalization gives shorter responses
disproportionately more gradient weight, which hurts math reasoning
tasks where correct answers often require detailed, longer derivations.
Global normalization weights all examples equally regardless of response
length.
"""

Fixes #

[wmoss]

• [Iris] Add sections to the UI for task stats #3
• [Iris] Store the task stats in sqlite #2
• [Zephyr] Send task stats from Zephyr to Iris #1 👈 (View in Graphite)
• main

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