Add secure, reopenable HTML artifact previews

[zenacquire]

What changed

• Added compact HTML creation cards that can expand while code is still streaming.
• Added persistent chat controls to open, close, and reopen the artifact that belongs to that message.
• Added a side-by-side, keyboard- and pointer-resizable artifact panel with cleanup on close.
• Isolated model-authored HTML with an opaque iframe sandbox and a restrictive srcdoc CSP that blocks outbound network access.
• Added Electron subframe navigation protection and trusted external-link handling.

Why

Generated HTML should behave like a reopenable artifact without letting model-authored scripts inherit application privileges or silently contact external hosts. The previous streaming and settled states also used different controls, which caused expansion and multi-artifact state bugs.

How it was verified

• pnpm test — 291 passed, 7 skipped
• pnpm build
• Component coverage for streaming expansion, settled reopen/close state, panel resizing, and cleanup
• Electron navigation-policy and HTML-sanitization/CSP coverage
• git diff --check codex/provider-configuration..HEAD

Screenshots (UI changes)

The artifact flow was manually exercised in the local Electron app during PR #74. This split retains only the HTML artifact implementation and its security boundary.

Checklist

• pnpm typecheck and pnpm test pass locally
• New behavior includes component and Electron policy tests
• No dist-server/ edits or dependency/lockfile churn
• macOS-only behavior remains Electron-gated
• Model-authored scripts cannot make outbound requests from the preview

Stack

• Depends on Add isolated OpenRouter and OpenAI-compatible providers #93 for the rebased provider foundation.
• Media generation and the Generations library follow as separate draft PRs.

This fork-based stack targets upstream main; this PR will be rebased after #93 lands so its visible diff collapses to this slice.

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Review details

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Configuration used: defaults

Review profile: CHILL

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Run ID: 3b69b5b8-baf8-4dc5-9c6c-b0e933102a8f

📥 Commits

Reviewing files that changed from the base of the PR and between 8490f3a and b37c184.

📒 Files selected for processing (32)

• README.md
• electron/main.mjs
• electron/navigation-policy.mjs
• electron/navigation-policy.test.mjs
• server/config.test.ts
• server/config.ts
• server/drivers/acp/acp.test.ts
• server/drivers/builtIn.ts
• server/drivers/ollama-cloud.ts
• server/drivers/openai-compatible.test.ts
• server/drivers/openai-compatible.ts
• server/drivers/openai-endpoint.ts
• server/drivers/openrouter.ts
• server/index.test.ts
• server/index.ts
• server/testing/fake-acp-cli.ts
• src/components/ApiKeys.tsx
• src/components/ArtifactPanel.test.tsx
• src/components/ArtifactPanel.tsx
• src/components/ChatMarkdown.test.tsx
• src/components/ChatMarkdown.tsx
• src/components/ChatView.tsx
• src/components/Onboarding.tsx
• src/components/OpenAIEndpointFields.tsx
• src/components/ProviderIcons.tsx
• src/components/ProviderSetupOptions.test.tsx
• src/components/ProviderSetupOptions.tsx
• src/components/SettingsModal.tsx
• src/lib/html-artifacts.test.ts
• src/lib/html-artifacts.ts
• src/state/store.tsx
• vite.config.ts

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