fix(workflow): recall generation graphs from images

[joshistoast]

Summary

Generate images already contain their execution graph, but Load Workflow only read an authored workflow and reported the workflow as missing. Fall back to converting the saved graph into an editable workflow, matching legacy behavior and supporting existing images.

Preserve metadata inputs and execution flags, normalize historical image-collection and frame-count values, and keep conversion behind the lazy graph-preview entry.

QA Instructions

From invokeai/frontend/webv2:

• pnpm lint — passed.
• pnpm test — 10,448 tests passed on the final candidate.
• pnpm test:browser — 2,969 tests passed. The initial run had an unrelated toast hover timeout; its 28 tests passed in isolation and the full browser rerun passed. The 62 image-action browser tests passed again after the final changes.
• pnpm test:fixtures — passed.
• pnpm test:performance:architecture — passed; production build budgets passed again after the compatibility fix. No baselines or budgets changed.
• pnpm test:project-files:browser and pnpm test:accessibility:browser — passed.

Reproduction: generate an image, open its context menu, and choose Load Workflow. The editor should open the image's saved graph rather than report a missing workflow. Authored workflows still take precedence.

The final production build was also checked with isolated browser fixtures: Load Workflow opened both recalled nodes with the saved prompt and no page errors. No GPU generation was run.

Review

Resolved metadata-key safety, eager-loading, and historical graph-input compatibility issues. No material findings remain. Regression coverage checks graph conversion through serialization and compilation, malformed graphs, template failures, and account/project changes while loading.

Compatibility / Rollout

Uses the existing embedded graph and workflow API. No backend, queue, persisted-schema, or migration changes are required. Unavailable node types retain the existing best-effort conversion warning.

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Meaningful regression coverage added / updated where needed; obsolete tests/code removed
• Persisted-state and API changes include required migrations / compatibility validation
• Relevant performance/efficiency opportunities considered; material claims have evidence
• Material review findings resolved and relevant checks rerun
• Documentation added / updated (if applicable) — affected loader and conversion contracts updated.
• Updated What's New copy (if doing a release after this PR) — not a release.

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[JPPhoto]

Great!