refactor(ui): extract markdown render owners

[Astro-Han]

Summary

• Governs packages/ui/src/components/markdown.tsx by extracting focused internal owners for sanitizing/fallback rendering, code block copy/link decoration, link/image click routing, task-list rewriting, and details state decoration.
• Keeps the public Markdown component and the existing test helper exports available from ./markdown.
• Reduces packages/ui/src/components/markdown.tsx from 598 LOC to 185 LOC.

Why

Owner lane: #601 message flow.

This is the final file-governance slice for this session. Markdown rendering is part of the message surface and had several unrelated responsibilities in one large component file. This PR makes that file reviewable without changing runtime behavior or package exports.

Related Issue

Related to #601 and #638.

Human Review Status

Pending. A human should make the final merge decision after reviewing the final diff and verification evidence.

Review Focus

• Confirm the extracted helpers preserve markdown sanitizing, task-list rendering, link routing, details open-state preservation, code block copy buttons, and inline code URL decoration.
• Confirm the PR only governs packages/ui/src/components/markdown.tsx and its same-directory internal helpers/tests.

Topology

• Base: dev
• Dependency status: independent flat PR; no parent or child PR.
• Review order: after chore: add frontend architecture governance baseline #667/chore(ui): add shared tool contract export #669 for governance context if desired, but independently mergeable once checks are green.
• This is the last new PR for the current goal window; no further worktrees or PRs will be opened from this session.

File Governed

Primary governed file:

• packages/ui/src/components/markdown.tsx

Supporting files:

• packages/ui/src/components/markdown-sanitize.ts
• packages/ui/src/components/markdown-code-tools.ts
• packages/ui/src/components/markdown-link-routing.ts
• packages/ui/src/components/markdown-task-list.ts
• packages/ui/src/components/markdown-details.ts
• packages/ui/src/components/markdown.test.ts

Behavior

Behavior intended unchanged. This is a structural extraction only. Public component usage remains Markdown from @opencode-ai/ui/markdown, and existing helper exports used by tests remain re-exported from ./markdown.

Tests Locking Behavior

The focused behavior tests cover:

• DOMPurify allow/deny behavior and protocol-relative URL rejection.
• GFM task-list checkbox sanitizing and SVG/label rewriting.
• link routing for external URLs, local paths, anchors, dangerous schemes, protocol-relative URLs, and Windows paths.
• code block copy button wrapping and idempotency.
• inline code URL decoration, existing-link preservation, and unwrap behavior when text is no longer URL-shaped.
• copy button failure handling plus timeout label reset behavior.
• details default-open behavior and user-collapse preservation.
• markdown streaming block behavior.

Testing Gap

No browser screenshot or Electron manual check was run because this PR is a same-behavior refactor of markdown internals with no intended visual, copy, route, IPC, or desktop shell change. Reviewers should still visually scan a rendered long assistant message if they want extra confidence in CSS/DOM parity.

Architecture Effect

• Owner extracted: sanitize/fallback, code tools, link routing, task list, and details decoration.
• LOC reduced: markdown.tsx 598 -> 185.
• Behavioral tests added: code block copy decoration, inline code URL mark/unmark behavior, existing-link preservation, and copy failure/timeout behavior.
• Public contract stabilized: existing ./markdown helper exports remain available.

Risk Notes

Behavior unchanged claim depends on the helper wiring preserving decorator order. The focused tests cover the highest-risk extracted behavior, but they do not replace a visual review of rendered markdown in the full app.

How To Verify

Diff overlap audit: no open PR touches packages/ui/src/components/markdown.tsx, markdown.test.ts, or the new markdown-* helper paths
LOC: packages/ui/src/components/markdown.tsx 598 -> 185
Focused tests: bun test src/components/markdown.test.ts src/components/markdown-stream.test.ts -> 44 passed
Typecheck: bun run typecheck in packages/ui -> tsgo --noEmit passed
Lint: bun run lint -- packages/ui/src/components/markdown.tsx packages/ui/src/components/markdown-sanitize.ts packages/ui/src/components/markdown-code-tools.ts packages/ui/src/components/markdown-link-routing.ts packages/ui/src/components/markdown-task-list.ts packages/ui/src/components/markdown-details.ts -> passed
Diff check: git diff --check -> clean

Screenshots or Recordings

Not run. No intended visible UI, copy, style, route, or desktop shell behavior change.

Checklist

• Human review status is stated above as pending, approved, or not required
• I linked the related issue, or stated why there is no issue
• This PR has type, primary area, and priority labels, or I requested maintainer labeling
• I described the review focus and any meaningful risks
• I listed the relevant verification steps and the key result for each
• I did not introduce unrelated refactors, dependencies, generated files, or file changes beyond the stated scope
• I manually checked visible UI or copy changes when needed, with screenshots or recordings
• I considered macOS and Windows impact for platform, packaging, updater, signing, paths, shell, or permissions changes
• I called out docs, release notes, dependencies, permissions, credentials, deletion behavior, generated content, or local file changes when relevant
• I reviewed the final diff for unrelated changes and suspicious dependency changes
• I am targeting dev, and my PR title and commit messages use Conventional Commits in English

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: de75096c-7640-4bec-9f3d-151386e09760

📥 Commits

Reviewing files that changed from the base of the PR and between 361d533 and 4e8457d.

📒 Files selected for processing (7)

• packages/ui/src/components/markdown-code-tools.ts
• packages/ui/src/components/markdown-details.ts
• packages/ui/src/components/markdown-link-routing.ts
• packages/ui/src/components/markdown-sanitize.ts
• packages/ui/src/components/markdown-task-list.ts
• packages/ui/src/components/markdown.test.ts
• packages/ui/src/components/markdown.tsx

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/ui-markdown-render-owners

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[github-actions]

Suggested priority: P2 (includes non-doc, non-test paths outside the low-risk bucket).

P1/P0 are reserved for maintainer confirmation. Please relabel manually if this is a release blocker, security issue, data-loss risk, or updater/runtime failure.

[gemini-code-assist]

Code Review

This pull request refactors the Markdown component by modularizing its logic into several specialized utility files, including markdown-code-tools.ts, markdown-details.ts, markdown-link-routing.ts, markdown-sanitize.ts, and markdown-task-list.ts. The feedback focuses on preventing invalid nested anchor tags when marking code links and improving the copy button handler with better memory management, i18n safety, and error handling for clipboard operations.

[github-actions]

Perf delta summary

Comparator: pass

Profile / Scenario	interaction median	interaction worst	long task max	tbt	frame gap p95	frame gap max	jank count	cls	status
default / homepage-cold	40 -> 24 (-16)	40 -> 64 (+24)	97 -> 64 (-33)	47 -> 14 (-33)	16.8 -> 16.8 (0)	166.6 -> 116.7 (-49.9)	4 -> 3 (-1)	0 -> 0 (0)	pass
default / long-session-input-lag	64 -> 48 (-16)	64 -> 48 (-16)	0 -> 0 (0)	0 -> 0 (0)	16.7 -> 16.7 (0)	16.7 -> 16.8 (+0.1)	0 -> 0 (0)	0 -> 0 (0)	pass
default / session-streaming-long	48 -> 40 (-8)	72 -> 72 (0)	0 -> 0 (0)	0 -> 0 (0)	16.8 -> 16.8 (0)	33.4 -> 33.3 (-0.1)	0 -> 0 (0)	0 -> 0 (0)	pass
default / tool-call-expand	24 -> 24 (0)	24 -> 24 (0)	0 -> 0 (0)	0 -> 0 (0)	16.8 -> 16.7 (-0.1)	16.8 -> 16.7 (-0.1)	0 -> 0 (0)	0 -> 0 (0)	pass
default / tool-default-open-heavy-bash	24 -> 24 (0)	32 -> 24 (-8)	65 -> 65 (0)	15 -> 15 (0)	50 -> 33.4 (-16.6)	116.7 -> 100.1 (-16.6)	3 -> 2 (-1)	0 -> 0 (0)	pass
default / terminal-side-panel-open	48 -> 48 (0)	64 -> 56 (-8)	0 -> 0 (0)	0 -> 0 (0)	33.3 -> 33.4 (+0.1)	33.3 -> 33.4 (+0.1)	0 -> 0 (0)	0 -> 0 (0)	pass
default / session-scroll-reading	24 -> 24 (0)	24 -> 24 (0)	0 -> 0 (0)	0 -> 0 (0)	16.8 -> 16.7 (-0.1)	16.8 -> 16.7 (-0.1)	0 -> 0 (0)	0.505 -> 0.505 (0)	warn: cls
low-end / session-scroll-reading-long	48 -> 56 (+8)	56 -> 64 (+8)	69 -> 80 (+11)	36 -> 46 (+10)	16.8 -> 16.8 (0)	216.6 -> 183.3 (-33.3)	3 -> 3 (0)	0.011 -> 0.011 (0)	pass
low-end / session-timeline-recompute	128 -> 120 (-8)	152 -> 128 (-24)	114 -> 109 (-5)	202 -> 168 (-34)	99.9 -> 99.9 (0)	183.4 -> 183.2 (-0.2)	3 -> 3 (0)	0.081 -> 0.081 (0)	pass
low-end / concurrent-shimmer-extreme	0 -> 0 (0)	0 -> 0 (0)	0 -> 0 (0)	0 -> 0 (0)	16.7 -> 16.8 (+0.1)	16.8 -> 16.8 (0)	0 -> 0 (0)	0 -> 0 (0)	pass