Fix nil-sceneId crash on advanced-auth browser callback for pre-scene logins (#4098)

[brandonpage]

What

Cherry-picks #4098 onto master. Original PR was merged to dev; this brings the same fix to the master branch.

Fixes a crash on the advanced-authentication browser callback for logins that start before any UIScene has connected — i.e. apps that begin login from AppDelegate.didFinishLaunchingWithOptions (hybrid and React Native).

Root cause

When login starts pre-scene, request.scene.session.persistentIdentifier is nil, so SFSDKAuthSession.sceneId was nil. On the ASWebAuthenticationSession completion handler, the SDK built an options dictionary keyed by the scene id (kSFIDPSceneIdKey) and looked the session back up in the authSessions store by that id. A nil key both crashed the dictionary insert and dropped the session from the store.

Fix

• SFSDKAuthSession.m — synthesize a unique per-session scene id (com.salesforce.mobilesdk.unscopedAuthSession-<UUID>) when no scene is connected.
• SFOAuthCoordinator.m / +Internal.h — extract option-building into -browserCallbackOptionsForSceneId: with a nil guard.
• SFOAuthCoordinatorTests.m — unit tests covering the scene-less login case.

Testing

• Cherry-picked the squash-merge commit cleanly onto master; resulting tree is byte-identical to the merged PR. No dev-only dependencies — all referenced symbols exist in the master baseline.
• SalesforceSDKCore test build succeeded; all 5 SFOAuthCoordinatorTests passed (0 failures), including the 4 new scene-less / nil-guard tests.

Work item

@W-23733618@

[github-actions]

	1 Error
🚫	Please re-submit this PR to the dev branch, we may have already fixed your issue.

Generated by 🚫 Danger

[github-actions]

	1 Warning
⚠️	Static Analysis found an issue with one or more files you modified. Please fix the issue(s).

Clang Static Analysis Issues

File	Type	Category	Description	Line	Col
SFOAuthCoordinator	Nullability	Memory error	nil assigned to a pointer which is expected to have non-null value	120	19
SFOAuthCoordinator	Nullability	Memory error	nil assigned to a pointer which is expected to have non-null value	244	15

Generated by 🚫 Danger

[github-actions]

	Tests	Passed ☑️	Skipped	Failed ❌️
SalesforceSDKCore iOS ^18 Test Results	631 ran	629 ✅		2 ❌

Test	Result
SalesforceSDKCore iOS ^18 Test Results
testNonCallbackURL()	❌ failure
SFUserAccountManagerTests.testUserAccountEncoding	❌ failure

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 66.85%. Comparing base (e816664) to head (17a2623).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...lesforceSDKCore/Classes/OAuth/SFOAuthCoordinator.m	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4122      +/-   ##
==========================================
- Coverage   66.91%   66.85%   -0.07%     
==========================================
  Files         260      260              
  Lines       22533    22536       +3     
==========================================
- Hits        15079    15066      -13     
- Misses       7454     7470      +16     

Components	Coverage Δ
Analytics	70.78% <ø> (ø)
Common	69.56% <ø> (-0.19%)	⬇️
Core	59.64% <83.33%> (-0.09%)	⬇️
SmartStore	74.70% <ø> (ø)
MobileSync	87.41% <ø> (ø)

Files with missing lines	Coverage Δ
...SalesforceSDKCore/Classes/OAuth/SFSDKAuthSession.m	91.42% <100.00%> (ø)
...lesforceSDKCore/Classes/OAuth/SFOAuthCoordinator.m	51.80% <66.66%> (+0.14%)	⬆️

... and 5 files with indirect coverage changes

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[github-actions]

	Tests	Passed ✅	Skipped	Failed
AuthFlowTester UI Test Results all	1 ran	1 ✅

Test	Result
No test annotations available