Use Zig for release cross builds

[scaryrawr]

Release builds currently depend on several host-specific CI paths, including Linux cross GCC and Windows MSVC-hosted compilation. This consolidates the release CLI builds around Zig so Linux-hosted CI can produce the cross-platform artifacts with fewer target-specific pipelines.

Summary

• Add checked-in Cargo linker config and Zig wrapper scripts for Linux GNU cross targets.
• Consolidate release compilation into a single Linux-hosted matrix for Linux and Windows CLI targets.
• Use cargo-zigbuild for Windows x86_64-pc-windows-gnu and aarch64-pc-windows-gnullvm builds instead of MSVC-hosted compilation.
• Update CPack installer lookup/output naming, remove obsolete reusable workflows and win-build.ps1, and document the new flow in README and Copilot guidance.

Validation

• cargo test
• cargo build --manifest-path=apps/sl/Cargo.toml --release --target x86_64-unknown-linux-gnu
• cargo build --manifest-path=apps/sl/Cargo.toml --release --target aarch64-unknown-linux-gnu
• cargo zigbuild --manifest-path=apps/sl/Cargo.toml --target x86_64-pc-windows-gnu
• cargo zigbuild --manifest-path=apps/sl/Cargo.toml --target aarch64-pc-windows-gnullvm
• CMake installer configuration for both Windows target output directories
• YAML, shell syntax, diff, and Prettier checks

[Copilot]

Pull request overview

This PR migrates the release build pipeline to use Zig as the cross-linker/toolchain driver so Linux-hosted CI can produce Linux and Windows CLI release artifacts with fewer platform-specific workflows.

Changes:

• Adds Zig-based linker wrapper scripts plus a checked-in .cargo/config.toml to drive Linux GNU cross-target linking via Zig.
• Consolidates release builds into a single Ubuntu-hosted cross-build matrix (Linux .deb + Windows NSIS installers) and removes the old Ubuntu/Windows reusable workflows and win-build.ps1.
• Updates Windows installer discovery and naming in CMakeLists.txt, and documents the new Zig-based flow in READMEs and Copilot guidance.

Show a summary per file

File	Description
win-build.ps1	Removes obsolete Windows build helper script.
scripts/zig-cc-x86_64-unknown-linux-gnu.sh	Adds Zig linker wrapper for x86_64-unknown-linux-gnu.
scripts/zig-cc-aarch64-unknown-linux-gnu.sh	Adds Zig linker wrapper for aarch64-unknown-linux-gnu.
scripts/zig-cc-linker.sh	Centralizes target-to-Zig-target mapping and dispatches to zig cc.
README.md	Documents Zig-based cross-compilation approach.
README.ja.md	Japanese documentation for Zig-based cross-compilation.
CMakeLists.txt	Adjusts installer artifact lookup and output naming for the new cross-build outputs.
.github/workflows/win-build.yml	Removes old Windows-hosted reusable workflow.
.github/workflows/ubuntu-build.yml	Removes old Ubuntu reusable workflow with GCC-based cross compilation.
.github/workflows/posix-build.yml	Removes old POSIX reusable workflow.
.github/workflows/build.yml	Adds Ubuntu-hosted cross-build matrix + macOS smoke job; updates release dependencies.
.github/copilot-instructions.md	Updates build-tool and CI guidance to reflect Zig/cargo-zigbuild usage.
.cargo/config.toml	Adds target-specific linker configuration pointing to Zig wrapper scripts.

Copilot's findings

• Files reviewed: 13/13 changed files
• Comments generated: 0