fix(git-status): landing fixes (#537)

- A cached list of repositories below a folder is re-checked against the
  Docker case workspaces as they are now, so a repository linked as a Docker
  workspace within the 30 s list cache is no longer inspected.
- A diff past runGit's 8 MB output bound is cut short from git's partial
  output instead of failing with a 500.
- The browser test waits for its slow route handler on unroute
  (unrouteAll behavior 'wait'), so a late route.continue() cannot fail the run.
- "Upstream is gone" now reads "Upstream not on remote", true for a branch
  that was never pushed as well as one deleted on the remote; docs mirrored.
- The diff route checks the repository against the workspace's own cached
  repository list (findWorkspaceRepo) and refreshes only that repository,
  instead of a fresh status of every repository in the folder.
- CLAUDE.md: a Key Patterns entry for the git read surface and its rules.
- The enclosing repository is identified with one cached rev-parse before
  any full status, so an unrelated repository above the workspace costs one
  process and its failure no longer hides the repositories below.
- Wiki: the bottom-bar indicator moves out of the header-controls table.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

test/git-status.browser.test.ts

@@ -389,7 +389,9 @@ describe('Git status indicator in a real browser', () => {
     await page.waitForFunction(() => !!(window as any).app._currentGitStatus());
     expect(await page.evaluate(() => (window as any).app._gitStatusInFlight)).toBe(false);
     page.setDefaultTimeout(30000);
-    await page.unroute('**/api/sessions/*/git-status*');
+    // The first read may still be asleep in the handler: wait for it to continue, or its late
+    // route.continue() lands after the route is gone and fails the run as an unhandled rejection.
+    await page.unrouteAll({ behavior: 'wait' });
     expect(await buttonVisible()).toBe(true);
     // Turning the setting off closed the panel; reopen it for the tests that follow.
     await page.click('#gitStatusBtn');