feat(api): reapply accepts the failed remainder of a partially completed apply

[aparajon]

Why this matters

The reapply endpoint (#698) requeues only a fully failed apply. Real failures are often partial — some tables completed before one failed — and forcing operators to hand-build a new apply for the remainder is exactly the toil reapply should remove.

What it does

• Replaces the strict all-failed shape guard with remaining-work selection: reapply gathers the apply's failed tasks, failed operations, and failed group finalizers, filters the stored plan down to that remainder, and requeues it when the fresh re-plan matches the remaining work.
• Completed work is never re-run: the plan comparison is against the failed remainder, so a re-plan that still includes completed tables is rejected as drift.
• Keeps the existing safety rejections — failed work outside the plan's primary deployment, and the fail-closed error for a failed task referencing a missing operation row.

Stacked on #698 (strict reapply endpoint). PR 3 of 5 in the reapply stack: storage primitive (merged) → strict endpoint (#698) → this → lock ownership → CLI.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds an operator-facing reapply control path to safely retry a failed schema change by re-planning against the current world state and only re-queueing when the fresh plan is equivalent to the remaining failed work.

Changes:

• Introduces POST /api/reapply route + handler wiring in the API service.
• Adds ReapplyResponse API type for the new endpoint.
• Implements reapply planning/equivalence logic plus unit tests around the core ExecuteReapply behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
pkg/apitypes/apitypes.go	Extends control-operation API types with a dedicated ReapplyResponse.
pkg/api/service.go	Wires the new POST /api/reapply handler into route registration and exported handler surface.
pkg/api/reapply_handlers.go	Implements handleReapply + ExecuteReapply with plan re-generation and equivalence checks before re-queueing failed work.
pkg/api/reapply_handlers_test.go	Adds tests covering reapply acceptance/rejection paths and plan filtering/equivalence helpers.

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