fix(kanban): preserve creator chat scope for terminal wakes

[worlldz]

Fixes #68874
Related to #56580

When a task is created from a direct message, the Kanban notifier can later wake the agent using a different session scope.

The notification itself reaches the correct chat, but the synthetic wake event was rebuilt with chat_type="group". DM and group conversations use different session keys, so the continuation could land in a fresh group session instead of the DM session that created the task.

This change:

• Persists the creator's chat_type on Kanban notification subscriptions.
• Adds a backward-compatible SQLite migration for existing databases.
• Carries chat_type through the session context bridge.
• Captures the source scope from /kanban create.
• Covers the tool auto-subscribe path as well.
• Uses the stored scope when rebuilding notifier wake events.
• Keeps the historical group fallback for legacy subscriptions.
• Avoids overwriting an already-captured chat scope.

Regression coverage includes DM wake routing, legacy database migration, chat type normalization, re-subscription behavior, and tool auto-subscription.

Validation:

162 passed

[alt-glitch]

This was generated by AI during triage.

Related to #68879 and #64113: all repair the persisted creator chat_type wake path. This version additionally covers tool auto-subscribe, so this is a competing broader implementation rather than a duplicate; please consolidate the preferred current patch.

[teknium1]

Superseded by PR #72191, which fixes this bug via #58615 (@ljsdut, earliest submission) plus the CLI call-site half of #64113 (@zmlgit). Your PR converged on the same design all four competing fixes landed on — chat_type persistence, group fallback, self-heal backfill — which is good corroboration that the design was right; it lost the arbitration only on submission date and auto-subscribe-path coverage. Thanks for the work, and the tests were solid.