[Ticket]: Split app/governance-ctl/src/sync.rs (1178 LoC)

### Type

Refactor

### Summary

`app/governance-ctl/src/sync.rs` is 1178 lines. Split it along its real seams to bring every resulting file under 200.

### Intent

It is one of the largest files in the repository and, at this size, is skimmed rather than reviewed.

### Source of truth (links)

- #162 (parent epic), #173 (baseline)

### Acceptance Criteria

1. No resulting file exceeds 200 LoC.
2. **Behaviour is unchanged** — the existing tests pass before and after, unmodified.
3. No test is weakened, deleted or made less specific to accommodate the split.
4. Module boundaries follow a real seam, not an arbitrary line count.
5. Public API unchanged, or the change is called out explicitly.

### Out of Scope

Behaviour changes of any kind. This is a pure refactor.

### Technical Context

The copilot-sync command. Seams: fetch, parse, upsert, manifest bookkeeping.

### Risks

⚠️ A shrinking file that also shrinks its assertions is a regression wearing a refactor's clothes. Reviewers should diff the test count and the assertion count, not just the line count.

### Test Plan

The existing suite, unmodified, before and after. If a test needed changing, say why in the PR — that is the signal worth reviewing.