feat: derive proactive traces from committed turns

[kachofugetsu09]

Result

• Remove the PROACTIVE_FINISHED special-event listener and its parallel trace projection.
• Record passive and ordinary Wake work exclusively from AFTER_TURN_COMMITTED.
• Preserve the existing dashboard schema: channel=wake maps to source=proactive; explicit channel=drift remains a generic channel classification only.
• Quiet Wake produces no delivered trace because it never reaches AfterTurn.

This PR does not deploy the plugin or remove Core's legacy event producer; the latter remains a later Core cleanup after all consumers migrate.

Verification

• Python: 16 passed
• Node: 5 passed
• Pyright: 0 errors
• Plugin API v3 contract at the workflow-pinned contract revision: passed
• git diff --check: passed
• Terra xhigh conceptual gate on f9cd7cdb91d05a1646cc15854509bacb628355d3: APPROVE, no must-fix

Recovery bundle: /mnt/data/coding/backups/observe-turn-committed-20260823/pre-migration-06e4f4b1.bundle