Migrate WGPU sonar backend from DAVE #44

[yeseorizi]

Purpose and provenance

Continue the WGPU sonar work in POSIM without replacing the current main tree.

• Original contribution and discussion: IOES-Lab/dave#44, opened by Naitik Pahwa (@naitikpahwa18).
• Source head: ca60ba63dcdf60cb76d231255570106e43024862.
• POSIM baseline merged into that branch: e05a9fb7d25ec21399f897e9bddfcabc4493b703.
• All 21 commits listed by the source PR remain in the ancestry with their original SHAs and author metadata, including subsequent contributions by Woen-Sug Choi and Yeseol Gwon. Original comments and reviews remain linked in DAVE; they are not recreated under another author's name.

What is carried over

The WGPU Rust/vendor package, compute shaders, C++ backend integration, optional CUDA support, BlueView model settings, demo guides, and existing range-axis validation assets. The current code includes later changes beyond the original PR description; this migration does not claim CPU fallback or new cross-platform runtime results.

POSIM integration decisions

• Keep POSIM's main-based workflows, ioeslab/posim image naming, repository manifests, documentation and installer fallback URL.
• Do not reintroduce the DAVE-only PR-image publisher or Pages deployment.
• Resolve the workflow conflicts in favor of POSIM's current policy; combine the source installer/Docker changes with POSIM branding and repository paths.
• Result: 38 changed files against the pinned POSIM baseline. The 36 source feature files outside the two workflows, ARM64 Dockerfile and installer are byte-identical to the source PR head.

Checks and remaining work

• Original source head and every listed source PR commit are ancestors of this branch.
• Current POSIM baseline is an ancestor; POSIM workflows and repository manifests are unchanged.
• git diff --check, changed Python syntax and installer Bash syntax pass.
• Four changed package XML files parse. The unchanged BlueView SDF uses the existing gz: extension; a generic XML parser reports an unbound-prefix warning. SDF/runtime validation is still required.
• Resolve integration with POSIM #5. A non-mutating merge preview finds an ARM64 Dockerfile conflict between the inherited ArduPilot retry block and Validate POSIM images and fix Docker runtime shutdown failures #5's runtime-image changes. Neither branch has been overwritten.
• Build and validate the POSIM-integrated sonar on the intended backends; retained validation assets are historical evidence, not a new test run.

Draft / CI note: migration commits use [skip ci] to avoid automatically starting long self-hosted builds before the imported code is reviewed. Repository CI/publication settings were not changed. Before marking this ready, push a follow-up commit without the skip marker and run the required CI/runtime checks. This PR is not a merge-ready or image-publication claim.

The original DAVE PR remains open until the migration is reviewed and closure is coordinated.