Preserve caller options when constructing an RFC2396 parser

[OskarEichler]

Summary

Copy the supplied option Hash and values before internal pattern construction deletes keys and freezes pattern strings. Preserve caller ownership while retaining immutable internal patterns.

Reproduction

With options = {ESCAPED: '%[0-9a-fA-F]{2}'}, constructing URI::RFC2396_Parser.new(options) empties the caller Hash. A frozen options Hash raises FrozenError. Afterward, both work without removing entries or freezing caller strings.

Verification

• Ruby 4.0.6 through rbenv; existing bundle exec rake test: 93 tests / 3,039 assertions / zero failures or errors, both baseline and this isolated patch.
• 32 checks cover empty/custom escape/unreserved/hostname patterns, frozen/mutable hashes, unchanged entries and value mutability, and successful parsing.
• Syntax and git diff --check pass. Supplemental Lint adds no findings against the 31-finding baseline.
• No test/spec files added or modified, per this contribution's explicit no-new-tests constraint. Focused reproductions ran externally.

Compatibility and limitations

Intentional ownership correction: caller options are retained. Hash#transform_values is supported by the existing Ruby >=2.5 minimum. Custom option-string validation is unchanged. No public API removal, dependency change or Ruby minimum change.

Based on master 696df43b0be4c05d3a0dcf7db582126c915d860d. Other Ruby/OS runtimes were not executed locally. No production traffic or live mail/FTP services were used. Existing related PRs/issues were checked; this is a focused contribution, not exhaustive behavioral coverage.