fix(postgresql): filter PITR archive roots

[weicao]

What

Filter PITR repository root listings to slash-terminated archive directories before child traversal.

Why

An unrelated root object ordered before a valid archive directory was treated as a directory; its list failure aborted fetch before the required WAL and handoff.

Tests

• RED f454e8984: Bash 3.2 focused 21 examples / 1 failure / 4 assertions
• GREEN: Bash 3.2 focused 21/0; Bash 5.3 PostgreSQL full 289/0
• Static/chart gates clean; render 41 docs / 1,014,408 bytes

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 0.00%. Comparing base (98a900a) to head (38f376c).

Files with missing lines	Patch %	Lines
...ns/postgresql/scripts-ut-spec/pitr_restore_spec.sh	0.00%	14 Missing ⚠️

Additional details and impacted files

@@                         Coverage Diff                          @@
##           easton/pg-pitr-restore-dual-data-dir   #3406   +/-   ##
====================================================================
  Coverage                                  0.00%   0.00%           
====================================================================
  Files                                       195     195           
  Lines                                     28416   28430   +14     
====================================================================
- Misses                                    28416   28430   +14     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.