feat(postgres): report the executor's live step from apply progress

[Kiran01bm]

PostgreSQL apply progress now reports the step pg-sprite's executor is actually running, and the statement text of that step, instead of a fixed step: 1.

Why

The engine published progress only at accept and at the terminal outcome, so a three-step create set reported step 1 of 3 from start to finish and a create that failed on its second index still said step 1. pg-sprite's executor already records every step it starts on a progress.Tracker; the engine just never gave it one.

What

• Apply creates one progress.Tracker per apply and threads it through executeOptimistic → ExecuteCreateWithProgress / ExecuteNativeWithProgress / BuildIndexConcurrentlyWithProgress.
• Tracked applies are trackedApply{result, tracker, logger}; publishProgress updates only the result.
• Progress snapshots the record under the engine lock, releases it, then overlays step, steps_total, and a sanitized statement from the tracker. The tracker read can touch the server's index-build progress view, so it never runs under e.mu; a failed read keeps the last-known position and logs under the apply's identifiers.
• For an active concurrent index build the tracker queries the session the executor reserved for the build's failure verdict, so the read runs on its own short-deadline context detached from the caller's cancellation — a cancelled poller or drive context must not tear that session down, and the deadline bounds how long a poll can hold the tracker's fence against the executor's own end-of-build stop.
• Every terminal result folds in the tracker's final position before publishing, so a later poll of a finished apply never re-reads the tracker.
• Pre-execution position stays step 1 / steps_total from the plan until the executor reports.

Not in scope, tracked as follow-ups: plumbing step / steps_total / statement through the drive layer and GET /api/progress/apply/{apply_id} so an operator surface actually renders them (today they terminate in the engine's progress record), and the attempt and concurrent-build work counters (blocks/tuples) the tracker also exposes.

Before / after

Before                                     After

Apply ── claim {step:1, total:3}           Apply ── claim {step:1, total:3} + tracker
  │                                          │
  ▼                                          ▼
executor runs steps 1..3                   executor runs steps 1..3 ─── StartStep(i) ──► tracker
  │        (nothing observes)                │                                              │
  │  poll ──► {step:1}                       │  poll ──► record ⊕ tracker ──► {step:2, statement}
  ▼                                          ▼
publish terminal {step:1}                  publish terminal ⊕ tracker ──► {step:3 | failed step}

[Copilot]

🟡 Changes recommended

The terminal progress publish path uses a cancellable apply context for reading tracker position, which can cause terminal step/statement metadata to fall back to the planned “step 1” when the apply ends due to cancellation/timeout.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR improves PostgreSQL apply progress reporting by wiring pg-sprite’s progress.Tracker through the apply execution path, allowing Progress to report the executor’s current step number, total steps, and the (sanitized) SQL statement for the in-flight step rather than always showing step: 1.

Changes:

• Thread a per-apply progress.Tracker through optimistic execution and overlay tracker-derived step/steps_total/statement onto progress snapshots.
• Preserve terminal apply progress by folding the tracker’s last-known position into the final published result, and avoid re-reading tracker state after terminal publish.
• Expand/update unit + integration tests to assert step/statement reporting and to refine invalid-index outcome messaging (including a new “other table” refusal test).

File summaries

File	Description
pkg/engine/postgres/postgres.go	Adds trackedApply and stores tracker + logger alongside published progress state for each apply.
pkg/engine/postgres/apply.go	Creates/threads a tracker through execution, overlays tracker position into Progress, and refines invalid-index refusal/operational classification.
pkg/engine/postgres/apply_test.go	Adds unit tests for tracker-backed step/statement reporting and extends invalid-index refusal/decision coverage.
pkg/engine/postgres/postgres_integration_test.go	Updates integration assertions for terminal step/statement metadata; adds new invalid-index-on-other-table refusal test.
go.mod	Bumps github.com/block/pg-sprite to v0.3.1.
go.sum	Updates checksums for the pg-sprite bump.
e2e/consumermodule/go.mod	Updates consumer module indirect pg-sprite version to v0.3.1.
e2e/consumermodule/go.sum	Updates checksums for the pg-sprite bump in the consumer module.

Review details

• Files reviewed: 6/8 changed files
• Comments generated: 1
• Review effort level: Lite

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