test: add macOS keychain test skeletons (1.3.1, 1.3.2, 3.5.8)

[jbair06]

Description:
Adds skeleton automation tests for the three macOS keychain manual test cases (1.3.1, 1.3.2, 3.5.8). Each test uses test.skip with inline TODOs describing the platform gate and page object methods that need to be implemented before these can run on macOS CI.

Related issue(s):

Fixes #3230

Checklist

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)

[swirlds-automation]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.98%. Comparing base (b23727b) to head (bd40e5a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3246   +/-   ##
=======================================
  Coverage   99.98%   99.98%           
=======================================
  Files         191      191           
  Lines        6175     6175           
  Branches     1124     1124           
=======================================
  Hits         6174     6174           
  Misses          1        1           

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