test(preview): restore cached image tests under jsdom

[ewen-poch]

Problem

#1643 (fix(host-sdk)!: camel-case public result fields) and #1648 (fix(settings): align package install controls with runtime ownership) merged with red PR Gate module shards. The failures were not from those diffs:

• test(settings-store): inventory deferred load facade locals #1649 already inventory-fixed the settings-store architecture guard.
• The remaining 18 unit failures came from perf(session-renderer): bound transcript rendering and cache images #1636's managed-image cache and windowed transcript rendering: jsdom Blob cannot be passed to Node's Response, so image tests never reached a ready <img>, and the architecture test still expected a linear conversationItems.map.

Proposed change

• Stub fetch with the { ok, status, blob() } shape the cache actually reads, instead of new Response(new Blob(...)).
• Wait for thumbnails to settle and assert cached blob: URLs for in-budget images.
• Pin transcriptWindow.entries.map(({ item, itemIndex }) as the scroller render loop.

No production code changes.

Scope and non-goals

Does not change Host SDK camelCase, package-install authorization UI, image cache eviction, or transcript windowing.

Compatibility notes

• Historical data compatibility: none. Preview image cache lives in renderer memory as blob URLs and is not persisted.
• New enum / status values: none.
• Data persistence: none. fix(settings): align package install controls with runtime ownership #1648 still stores historical user-owned R installAuthorized values and ignores them in the UI; this PR does not touch that.

Acceptance criteria and validation

All checks below ran after the last material edit:

• Cached image and transcript architecture regressions -> npm test -- src/renderer/src/pages/workspace/preview-image-content.test.tsx src/renderer/src/pages/workspace/artifact-preview.interaction.test.tsx src/renderer/src/pages/workspace/previews/PreviewFileContent.test.tsx src/renderer/src/pages/workspace/workspace-components.test.tsx src/renderer/src/components/global-search/GlobalSearchDialog.test.tsx src/renderer/src/pages/workspace/ProjectFilesView.test.tsx src/renderer/src/stores/settings-store.architecture.test.ts -> 7 files, 206 tests passed.
• project_files_view module tests -> npm run test:module -- project_files_view -> 6 files passed.
• External PR owner tests (unchanged by this branch) -> npm test -- src/main/host-sdk/delegate-contract.test.ts src/main/host-sdk/help.test.ts src/renderer/src/pages/settings/RuntimesPanel.render.test.tsx -> 3 files, 51 tests passed.
• Lint of changed files -> npx eslint on the 7 touched files -> no issues.
• Diff hygiene -> git diff --check -> passed.

Full portable npm test was not run locally; PR Gate remains authoritative.

Review focus

Please focus on the fetch stub matching useCachedPreviewImage (ok / blob() only) and the thumbnail assertions now expecting blob: URLs for images under the 64 MiB cache budget.

[github-actions]

Codex Review

Verdict: mergeable

No actionable findings.

Summary: Static inspection found no concrete merge-blocking defect in the pull-request changes.