[codex] Polish issue board workflows (#4224)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - Human operators supervise that work through issue lists, issue
detail, comments, inbox groups, markdown references, and
profile/activity surfaces
> - The branch had many small UI fixes that improve the operator loop
but do not need to ship with backend runtime migrations
> - These changes belong together as board workflow polish because they
affect scanning, navigation, issue context, comment state, and markdown
clarity
> - This pull request groups the UI-only slice so it can merge
independently from runtime/backend changes
> - The benefit is a clearer board experience with better issue context,
steadier optimistic updates, and more predictable keyboard navigation

## What Changed

- Improves issue properties, sub-issue actions, blocker chips, and issue
list/detail refresh behavior.
- Adds blocker context above the issue composer and stabilizes
queued/interrupted comment UI state.
- Improves markdown issue/GitHub link rendering and opens external
markdown links in a new tab.
- Adds inbox group keyboard navigation and fold/unfold support.
- Polishes activity/avatar/profile/settings/workspace presentation
details.

## Verification

- `pnpm exec vitest run ui/src/components/IssueProperties.test.tsx
ui/src/components/IssueChatThread.test.tsx
ui/src/components/MarkdownBody.test.tsx ui/src/lib/inbox.test.ts
ui/src/lib/optimistic-issue-comments.test.ts`

## Risks

- Low to medium risk: changes are UI-focused but cover high-traffic
issue and inbox surfaces.
- This branch intentionally does not include the backend runtime changes
from the companion PR; where UI calls newer API filters, unsupported
servers should continue to fail visibly through existing API error
handling.
- Visual screenshots were not captured in this heartbeat; targeted
component/helper tests cover the changed behavior.

> For core feature work, check [`ROADMAP.md`](ROADMAP.md) first and
discuss it in `#dev` before opening the PR. Feature PRs that overlap
with planned core work may need to be redirected — check the roadmap
first. See `CONTRIBUTING.md`.

## Model Used

- OpenAI Codex, GPT-5-based coding agent runtime, shell/git tool use
enabled. Exact hosted model build and context window are not exposed in
this Paperclip heartbeat environment.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

ui/src/components/MarkdownBody.test.tsx

@@ -225,6 +225,51 @@ describe("MarkdownBody", () => {
     expect(html).toContain('style="overflow-wrap:anywhere;word-break:break-word"');
   });
 
+  it("opens external links in a new tab with safe rel attributes", () => {
+    const html = renderMarkdown("[docs](https://example.com/docs)");
+
+    expect(html).toContain('href="https://example.com/docs"');
+    expect(html).toContain('target="_blank"');
+    expect(html).toContain('rel="noopener noreferrer"');
+  });
+
+  it("opens GitHub links in a new tab", () => {
+    const html = renderMarkdown("[pr](https://github.com/paperclipai/paperclip/pull/4099)");
+
+    expect(html).toContain('target="_blank"');
+    expect(html).toContain('rel="noopener noreferrer"');
+  });
+
+  it("does not set target on relative internal links", () => {
+    const html = renderMarkdown("[settings](/company/settings)");
+
+    expect(html).toContain('href="/company/settings"');
+    expect(html).not.toContain('target="_blank"');
+    expect(html).toContain('rel="noreferrer"');
+  });
+
+  it("prefixes GitHub markdown links with the GitHub icon", () => {
+    const html = renderMarkdown("[https://github.com/paperclipai/paperclip/pull/4099](https://github.com/paperclipai/paperclip/pull/4099)");
+
+    expect(html).toContain('<a href="https://github.com/paperclipai/paperclip/pull/4099"');
+    expect(html).toContain('class="lucide lucide-github mr-1 inline h-3.5 w-3.5 align-[-0.125em]"');
+    expect(html).toContain(">https://github.com/paperclipai/paperclip/pull/4099</a>");
+  });
+
+  it("prefixes GitHub autolinks with the GitHub icon", () => {
+    const html = renderMarkdown("See https://github.com/paperclipai/paperclip/issues/1778");
+
+    expect(html).toContain('<a href="https://github.com/paperclipai/paperclip/issues/1778"');
+    expect(html).toContain('class="lucide lucide-github mr-1 inline h-3.5 w-3.5 align-[-0.125em]"');
+  });
+
+  it("does not prefix non-GitHub markdown links with the GitHub icon", () => {
+    const html = renderMarkdown("[docs](https://example.com/docs)");
+
+    expect(html).toContain('<a href="https://example.com/docs"');
+    expect(html).not.toContain("lucide-github");
+  });
+
   it("keeps fenced code blocks width-bounded and horizontally scrollable", () => {
     const html = renderMarkdown("```text\nGET /heartbeat-runs/ca5d23fc-c15b-4826-8ff1-2b6dd11be096/log?offset=2062357&limitBytes=256000\n```");