feat(desktop): refine repository-aware project workspaces (#6003)

## Summary
- Makes Projects repository-aware across browsing, branch and tag
selection, local and remote source management, work items, commits, and
contextual repository actions.
- Refines project details into consistent single-column reading surfaces
with a resizable, section-aware context pod, while keeping project
conversations available in the attached chat panel.
- Adds persistent sidebar project navigation, direct entity links,
repository discussion channels, contributor identity matching, and
consistent loading and activity presentation.
- Keeps branch-specific controls on code-oriented sections while Tasks,
Reviews, and Channels remain repository-scoped, reducing misleading
context and actions.

Replacement for #5981 with an identical final tree flattened into one
signed-off commit because the required DCO check suite remained stalled.

### Related issue
N/A

### Testing
- [x] Desktop pre-push checks, TypeScript typecheck, and unit tests
- [x] E2E production build with `pnpm build:e2e`
- [x] Focused Playwright smoke coverage for project workspace, task,
review, commit, sidebar, and contextual-panel behavior
- [ ] Attach final before/after screenshots after design review

---------

Signed-off-by: Thomas Petersen <thomasp@squareup.com>
Signed-off-by: Wintermute <165f0c871dd2586bb18b6aa109eeaf57bb2132ff4d27b10120f4368a0f627022@buzz.block.builderlab.xyz>
Co-authored-by: Wintermute <165f0c871dd2586bb18b6aa109eeaf57bb2132ff4d27b10120f4368a0f627022@buzz.block.builderlab.xyz>

desktop/src/shared/ui/markdown/nodeCache.test.mjs

@@ -207,6 +207,26 @@ test("oversized content bypasses the cache", () => {
   assert.notEqual(first, second);
 });
 
+test("hardLineBreaks changes the parse and the cache key", () => {
+  clearMarkdownNodeCache();
+  const content = "hello\nworld";
+  const withBreaks = renderCachedMarkdown({ ...BASE, content });
+  const withoutBreaks = renderCachedMarkdown({
+    ...BASE,
+    content,
+    hardLineBreaks: false,
+  });
+  assert.notEqual(withBreaks, withoutBreaks);
+  assert.match(renderToStaticMarkup(withBreaks), /<br/i);
+  assert.doesNotMatch(renderToStaticMarkup(withoutBreaks), /<br/i);
+  const withoutBreaksAgain = renderCachedMarkdown({
+    ...BASE,
+    content,
+    hardLineBreaks: false,
+  });
+  assert.equal(withoutBreaks, withoutBreaksAgain);
+});
+
 test("active search queries bypass the cache", () => {
   clearMarkdownNodeCache();
   const first = renderCachedMarkdown({ ...BASE, searchQuery: "bold" });