LDA-1802: fix fenced examples and validate PAR namespaces

[Marco-03]

Summary

• ignore ordered-list content inside fenced Markdown examples when enforcing four-space indentation
• reject newly added OCI Object Storage PAR URLs unless the namespace is c4u04 or c4uo2
• validate only added PR lines and avoid printing PAR bearer tokens
• add regression tests for approved, rejected, malformed, templated, and diff-only cases

Validation

• PAR validator unit tests: 5 passed
• OCI PR 613 regression: the original unindented fenced example now passes
• genuine unindented code blocks inside real numbered steps still fail
• git diff --check passed