feat(api): status folds surface the deployment's shared data-plane apply id

[aparajon]

Why this matters

When an operator filters status by deployment, an apply that ran per shard folds its operations into one synthetic row — and that row carried no external id at all. The one identifier the northstar guarantees (one deployment → one data-plane apply) vanished exactly where the operator looks for it during an incident. The single-operation shapes already surfaced their id; the folded shape lost it.

What it does

• The status fold resolves the deployment's shared data-plane apply id via a new strict resolver, storage.DeploymentExternalID, and carries it on the folded row. Per-operation external ids stay out of the summary — they belong to the per-shard detail views, so the folded row's external operation id is empty.
• The strict resolver reads the external_id column only. The legacy engine-resume-context carrier is deliberately excluded on this read path: locally driven operations store engine-owned resume state there, not an apply id, and the fold covers local applies too. DeploymentRemoteApplyID (the write-path resolver, legacy carrier honored) and the strict variant now share one core.
• Divergent ids across one deployment's operations are never guessed at: the response omits the external id and the divergence is logged server-side with the apply's triage identifiers.

How it moves us toward the northstar

One data-plane apply per deployment; operations dispatch into it.

0  per-shard reconcile                          ✅ shipped
pre vschema-only deployment-scoped shape        ✅ shipped
pre op-lease drives settle projection-safely    ✅ shipped
1  dispatch granularity
   ├─ data-plane sibling attach                 ✅ merged
   └─ deployment-keyed idempotency + echo       ✅ merged
2  correlation persistence                      🔍 in review
3  op-scoped data-plane drive (shared apply)    verified in step 6
4  read model exposes the deployment apply id   ⬅ this PR
5  CLI renders it as APPLY ID in deployment mode
6  test matrix

Opened by Claude (Fable 5).