Exclude React-version selection glue from coverage (fix codecov/patch on master)

[adeelraza]

Fixes the red codecov/patch check on master (introduced by #514). No build or test was ever broken — this is a coverage-gate artifact.

Cause

#514 added the useId/counter selection ternary for the SSR editor-id fix. In any single coverage run one arm is always unreachable:

• the run uses React 18/19, so typeof React.useId === 'function' is true and the counter fallback arm never executes;
• the React 16/17 path that would hit it is the test:legacy smoke suite, which runs without coverage by design (@testing-library/react needs React 18+).

So line 33 is a partial branch on a new line → codecov/patch < 100% → red.

Fix

The fallback function was already v8 ignore-d; this extends the ignore over the selection ternary itself. Comment-only — no logic changes.

Verification (local)

• EmailEditor.tsx branch coverage 94.28% → 96.96%; line 33 no longer reported. The only remaining uncovered branch is the pre-existing typeof window SSR guard (line 16), which isn't part of any patch, so it won't trip codecov/patch.
• npm test (12/12), npm run typecheck, npm run lint — clean.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.43%. Comparing base (3a9fff2) to head (7ce7093).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #516      +/-   ##
==========================================
+ Coverage   96.25%   97.43%   +1.18%     
==========================================
  Files           2        2              
  Lines          80       78       -2     
  Branches       20       20              
==========================================
- Hits           77       76       -1     
+ Partials        3        2       -1     

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