Consolidate and run upstream Mike synchronizers - #41

What changed

• removes the duplicate PR Add bounded bulk Mike synchronizer #39 low-risk synchronizer, its separate cursor/ledger, documentation, and dedicated regression test;
• retains the coherent PR Add bulk upstream Mike synchronizer #38 low-risk producer and PR Automate medium and high risk upstream Mike batches #40 medium/high-risk consumer;
• adds one ordered runner that dispatches low risk first, waits for any generated synchronization PR to merge, and then dispatches the escalated medium/high pass;
• includes a request marker so the ordered runner starts immediately after this installer merges.

Resulting workflow model

1. Synchronize low-risk upstream Mike changes
2. Synchronize escalated upstream Mike changes
3. Run all upstream Mike synchronizers as the manual/one-shot orchestrator

The two synchronization lanes no longer compete or maintain independent cursors.

Safety

The ordered runner has only Actions write plus repository and pull-request read permissions. It does not create patches, merge PRs, or deploy. Existing exact-head Baseline, repair, review-thread, mergeability, and high-risk draft gates remain authoritative.

Immediate run

Merging this PR changes docs/upstream-sync-request.json, which triggers the ordered runner on main.