SaveAsReproducible method

Rewrites the document so that two saves of the same in-memory state produce byte-identical output

Object order is already stable (ascending object number), and the content-hash /ID derivation is deterministic, so the remaining non-determinism is the wall-clock /CreationDate and /ModDate that PDFium writes into /Info

StripDictionaryEntries removes those timestamp keys from the /Info body, and the rebuilt trailer omits the source /ID (which derives from time-stamped bytes)

Unreachable objects are also swept exactly like SaveAsReachable, and object numbers and generations stay stable

• TPdfReproducibleReport reports kept and pruned object counts plus the number of stripped timestamp entries
• Encrypted documents are rejected because content streams are ciphertext
• Signed documents are rejected unless AllowSignedDocument is explicitly enabled because a full rewrite invalidates existing signature byte ranges
• The output omits /ID entirely; callers that need a stable identifier can derive one from the output bytes

SaveAsReachable, SaveAs, SaveAsDeduplicated