First-class methodRunId / invocationId on DataRecord

Problem

After PR #1145 promoted workflow provenance fields (workflowRunId, workflowName, jobName, stepName, source, ownerRef) to first-class DataRecord fields, one provenance dimension is still missing: the identity of the specific method invocation that produced a record.

Workflows have workflowRunId. Workflow steps have stepName + jobName. But a single method invocation — whether triggered by swamp model method run or by a workflow step — has no identifier on its outputs. Two invocations of the same method on the same model produce records that are indistinguishable except by createdAt (per-record, not per-invocation) or version (per-data-name, doesn't correlate across data names).

What's missing

A methodRunId (or invocationId) field, peer to workflowRunId. Properties:

• Generated by the framework at the start of every method invocation, manual or workflow-triggered
• Set on every data record the invocation produces
• First-class queryable: in QUERY_FIELDS, indexed in the catalog, populated during backfill
• Always populated — never empty

Same shape of change as PR #1145.

What it unlocks

# All data from a specific invocation
methodRunId == "abc-123"

# Per-item records from the latest run of a model
modelName == "X" && methodRunId == data.latestMethodRunId("X")

The latter case is the one that has no clean expression today. Workarounds (batch manifests, createdAt clustering, per-extension tagging conventions) all push a missing primitive into the extension layer.

Why this is not "execution identity scoping"

Earlier discussion (#1123) rejected automatic scoping by execution identity. That was about hidden framework-injected filters. This is the opposite: methodRunId is a plain queryable field that authors compose into predicates explicitly. No auto-injection. The framework's job is just to expose the field.

Out of scope

• Per-invocation execution metadata beyond identity (timestamps, duration, status) — separate
• A data.latestMethodRunId(modelName) helper — sugar that could come later