feat(portability): complete v1.9.6 portability and distribution

Review boundary

This change adds evidence and qualification infrastructure; it does not change the public API or numerical algorithms.

• Add a versioned target/support contract, native Pascal ABI/binary probe, and offline Python validator/source-package audit.
• Require verified clean source archives and extracted checked offline HTML in release qualification.
• Run primary checks on changes, secondary Win32 checks at their documented scope, and complete Linux/Windows archive qualification weekly and for exact candidates/releases.
• Publish support, audit, limitation, installation, release, and qualification documentation for 1.9.6.

Required review checks

1. Tests reject missing target evidence, inferred unqualified ABIs, mismatched native observations, unsafe archives, compiler outputs, and checksum errors. 2. The native fixture remains byte-identical and locale-independent on each qualified target while ABI-dependent Extended storage is explicit. 3. Network blocking is applied only after toolchain installation and restored before artifact publication. 4. The frozen 1.9 public snapshot remains exact and no stable source adds a foreign runtime dependency.

Explicit exclusions

• No macOS/ARM64 or Linux/ARM64 support claim without maintained runner evidence.
• No new package manager, generated source, public declaration, CPU-specific numerical kernel, or mandatory external tool.
• No claim that retained v1.9.5 evidence replaces exact 1.9.6 candidate CI.