fix(core): detect Oculus Browser instead of falling back to Chrome

[Ashut0sh-mishra]

Problem

Events generated on Meta Quest headsets are reported with browser Chrome
instead of Oculus because the Oculus Browser user agent contains both
OculusBrowser and Chrome (and on newer firmware also SamsungBrowser),
and the existing detection order returns the first matching branch.

Closes #3574

Fix

• Add OculusBrowser detection in detectBrowser before the
  SamsungBrowser / Chrome branches in packages/core/src/utils/user-agent-utils.ts.
• Add a corresponding entry in versionRegexes so detectBrowserVersion
  returns the actual Oculus Browser version.
• Constants follow the existing pre-uglifying string-concatenation style noted
  in the file header comment.

Tests

Added two new cases to packages/browser/src/__tests__/utils/user-agent-utils.test.ts:

• Quest 2 UA (older format, with SamsungBrowser segment).
• Quest 3-style UA (no SamsungBrowser segment).

Both assert expectedBrowser: 'Oculus Browser' and the correct
expectedVersion, exercising the same detectBrowser / detectBrowserVersion
suite the other browsers in this file go through.

Reference UA list: https://whatmyuseragent.com/browser/oc/oculus-browser

[vercel]

@Ashut0sh-mishra is attempting to deploy a commit to the PostHog Team on Vercel.

A member of the Team first needs to authorize it.

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
packages/core/src/utils/user-agent-utils.ts:52-53
The `OCULUS` constant is only used once — to build `OCULUS_BROWSER`. The file header explains that intermediate constants exist for minification of *repeated* strings; `'Oculus'` doesn't appear anywhere else, so the intermediary adds a part with no benefit (simplicity rule #4). By contrast, the `'OculusBrowser'` UA token that appears twice in the file (detection check + version regex) was not factored out.

```suggestion
const OCULUS_BROWSER = 'Oculus Browser'
```

_{Reviews (1): Last reviewed commit: "fix(core): detect Oculus Browser instead..." | Re-trigger Greptile}

[Ashut0sh-mishra]

Thanks @greptile-apps! Inlined OCULUS directly into OCULUS_BROWSER -- you're right, it was only used once. Pushed.

[greptile-apps]

That's the clean approach — one less constant to track. The fix looks good overall. Thanks for the quick iteration!

Tip: You can customize Greptile's behavior for this repo with .greptile/rules.md and .greptile/config.json.

[greptile-apps]

_{Reviews (2): Last reviewed commit: "refactor(core): inline OCULUS constant i..." | Re-trigger Greptile}

[greptile-apps]

Looks great — the inlined version is cleaner. The diff is in good shape:

• OCULUS_BROWSER = 'Oculus Browser' is defined once and used in both detectBrowser and versionRegexes
• The OculusBrowser string literal in the regex and includes() check is fine since it's a UA token, not a display name
• Detection order is correct (before SamsungBrowser and Chrome)
• Both test cases cover the right scenarios

LGTM.