feat: development hardening

[fahad19]

Summary

Prepares Java SDK 0.3.0 with runtime behaviour aligned to the updated JavaScript SDK.

Changes

• Correct lazy ICU branch evaluation, quoting and missing argument handling.
• Improve plural precision and effective formatting options.
• Strengthen datafile validation, merging and ownership.
• Fix module removal, failed setup cleanup and concurrent shutdown.
• Preserve child-owned events, subscriptions and resolver resources.
• Expand portable conformance and strict example checks.
• Update documentation and all release coordinates to 0.3.0.

Verification

• 104 unit tests passed.
• Build, Javadoc and publication artifact verification passed.
• CLI reports 0.3.0.
• Release workflow version validation passed.
• 1,342 shared project assertions and 2,028 strict examples passed.