chore(tools): add shader-refactor bytecode verifier

[alandtse]

Adds tools/verify-shader-refactor.ps1 (+ tools/verify-shader-refactor.sh wrapper) to programmatically prove an HLSL refactor changed no behavior.

What it does

Compiles a shader from a base git ref and from the working tree across the VR × HDR_OUTPUT permutations, then compares the compiled DXBC:

• IDENTICAL SHA-256 of the .cso ⇒ provable no-op (fxc emits no timestamps without /Zi).
• DIFFERS ⇒ dumps + diffs the /Fc assembly for review.

Exit 0 all identical / 2 some differ / 1 compile error. Default base = merge-base(HEAD, origin/dev); -BaseRef overrides. Auto-detects entry/profile (*CS.hlsl → cs_5_0, else ps_5_0). Requires fxc.exe from the Windows SDK.

Tested

• Detects real change: TAA VR fix (fix(TAA): restore VR per-eye reprojection and opaque alpha #84) → PSHADER/PSHADER HDR_OUTPUT IDENTICAL, VR perms DIFFERS, exit 2 (with asm diff).
• Confirms no-op: TAA constants/alpha-loop refactor (refactor(TAA): name decompile constants and loop alpha coverage #85) → all four permutations IDENTICAL, exit 0.
• Both PowerShell and bash entry points exercised; Windows PowerShell 5.1 compatible (no pwsh/.NET-Core-only APIs).

Caveat

The fixed permutation sweep is strong evidence, not the full shader-validation.yaml matrix — -Permutations handles exotic define combos.

🤖 Generated with Claude Code

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: b1167fc1-fcb6-4e35-a237-29fbb6d9dc35

📥 Commits

Reviewing files that changed from the base of the PR and between 629b1d2 and 26ef2b5.

📒 Files selected for processing (4)

• .claude/CLAUDE.md
• docs/development/shader-workflow.md
• tools/verify-shader-refactor.ps1
• tools/verify-shader-refactor.sh

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/shader-refactor-verifier

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[Copilot]

Pull request overview

Adds a small verification toolchain to help shader authors confirm that “refactor-only” HLSL edits are behavior-preserving by comparing compiled DXBC output between a base git ref and the working tree.

Changes:

• Introduces tools/verify-shader-refactor.ps1 to compile shader permutations and compare .cso hashes, with /Fc assembly diff output on mismatches.
• Adds a bash wrapper (tools/verify-shader-refactor.sh) for bash/WSL/git-bash entry points that forwards args into the PowerShell script.
• Documents the workflow in docs/development/shader-workflow.md.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
tools/verify-shader-refactor.ps1	Core implementation: compile base/worktree permutations, hash-compare DXBC, print assembly diffs on mismatch.
tools/verify-shader-refactor.sh	Bash wrapper to invoke the PowerShell verifier from bash-like shells.
docs/development/shader-workflow.md	Adds usage/docs for verifying shader refactors via the new tool.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.