fix(sbom): harden bounded lineage input privacy

[tcconnally]

Summary

• Harden SBOM lineage raw-document and external-edge boundaries against attacker-raised exceptions and exception-text disclosure.
• Enforce exact, case-sensitive XML namespace admission before SPDX RDF/non-RDF parser selection.
• Reject foreign/case-variant SPDX namespaces, evil-namespaced package children, and foreign RDF descendants while preserving official SPDX RDF and CycloneDX fixtures.
• Preserve raw input bytes on Windows with O_BINARY, preventing CRLF translation from invalidating ingestion digests.
• Add direct regression coverage for hostile inputs, raw-document rebinding, edge sequences, malformed normalized formats, namespace bypasses, and Windows portability.

Verification

• tests/test_sbom_lineage.py: 141 passed
• Full suite: 2758 passed, 6 skipped
• scripts/build.py --check: passed
• Fresh exact-tree review deleg_94ad7e88: passed with empty security and logic findings
• Exact-head Windows CI failure on the preceding candidate was reproduced and fixed with O_BINARY; the corrected portability probe preserves the native flag.

Exact candidate evidence

• Candidate: 761ca6e78607a3fcf88a656bd3c999c3545ea3f1
• Source/test commit: 994edca
• Reviewed base: da2025e8d61893ac67dbe0aa2f9a69274ce8ef7a
• Tree SHA-256: 52485b98464ed2ae792acf5bc885638c6dccacab2f5b7260f9c153583a8f49b8
• Patch SHA-256: 3678ef5c9388d0767ef0a86f5d215c1e5433a3c92aaa1ae28e39919463029da9
• Tracked paths: 1228

Fixes #995