PatternSyntaxException when template uses nested Xray iterator TestExecutions[n].TestRuns[n].<field>

Summary

When a template contains a nested Xray iterator mapping of the form
TestExecutions[n].TestRuns[n].<field>, Xporter builds an *internal regex
pattern* with a stray closing parenthesis. The resulting
PatternSyntaxException aborts the "getting test plans info from Xray"
pipeline, which silently breaks any data resolved through that path
(Pre-Conditions, linked Tests, embedded images/attachments coming from
Xray-related issues).

The user-facing template syntax is correct; the malformed pattern is generated
internally by the mapping engine.

Environment

• Xporter for Jira 7.4.3-j10
• Jira Data Center 10.3.8 (Java 17)
• Xray DC (any recent version)

Steps to reproduce

1. Have a Test Plan with at least one Test Execution that contains Test Runs.
2. Create a Xporter template that includes a nested mapping such as:

   #{for TestExecutions}
      #{for TestRuns}
          ${TestExecutions[n].TestRuns[n].Key}
      #{end}
   #{end}
   

3. Trigger the export against the Test Plan issue.
4. Inspect atlassian-jira.log (DEBUG on com.xpandit.plugins.xporter is enough).

Expected behaviour

The template renders the Test Run keys for every Test Execution under the
Test Plan, and the rest of the Xray-related data (Pre-Conditions, linked
Test attachments, etc.) is resolved normally.

Actual behaviour

The following error is logged and the Xray pipeline aborts:

ERROR [c.x.j.mapping.a.w] An error has occurred while Xporter is getting
test plans info from Xray: Unmatched closing ')' near index 41
    TestExecutions\[\d+\].TestRuns\[\d+\].Key')
                                             ^
java.util.regex.PatternSyntaxException: Unmatched closing ')' near index 41
TestExecutions\[\d+\].TestRuns\[\d+\].Key')
                                         ^
    at java.base/java.util.regex.Pattern.error(Unknown Source)
    at java.base/java.util.regex.Pattern.compile(Unknown Source)
    at java.base/java.util.regex.Pattern.<init>(Unknown Source)
    at java.base/java.util.regex.Pattern.compile(Unknown Source)
    at com.xpandit.jiraxporter.mapping.a.w.a(Unknown Source)
    at com.xpandit.jiraxporter.mapping.a.w.a(Unknown Source)
    ...
    at com.xpandit.jiraxporter.manager.impl.XporterFieldRetrieverImpl
        .lambda$getFieldRetriever$193(Unknown Source)
    at com.xpandit.jiraxporter.mapping.c.a(Unknown Source)
    at com.xpandit.jiraxporter.mapping.g.a(Unknown Source)
    at com.xpandit.jiraxporter.utils.DocumentBuildLookup.lookup(Unknown Source)
    at com.xpandit.jiraxporter.component.service.XporterServiceImpl
        .exportIssue(Unknown Source)

The malformed pattern is TestExecutions[\d+].TestRuns[\d+].Key') — note
the trailing ') that should not be there.

Side effects observed

Because the failing pipeline is the same one that resolves Xray-related data
under a Test Plan, this bug can transitively cause:

• Pre-Condition embedded images / attachments not appearing in the report.
• Attachments stored at the linked Test level not