Fix duplicate native DLLs in net4x output directory

[shimat]

Fixes #1765

Problem

When a .NET Framework (net4x) project references OpenCvSharp4.runtime.win or OpenCvSharp4.runtime.win.slim via PackageReference, two separate mechanisms both copy the native DLLs into the build output:

1. The .props file (imported via build/netstandard/) copies them to dll/x64/, where WindowsLibraryLoader looks at runtime.
2. NuGet's PackageReference pipeline also copies runtimes/win-x64/native/ assets to the output root as part of its native asset resolution.

The root copies are never loaded by OpenCvSharp and serve no purpose, but they inflate the output directory and can interfere with deployment tooling that packages everything in the output folder.

Fix

Add a .targets file for each runtime package (OpenCvSharp4.runtime.win and OpenCvSharp4.runtime.win.slim) that runs after ResolvePackageAssets and removes the package's entries from RuntimeCopyLocalItems when targeting net4x. This suppresses the redundant root copy. The dll/x64/ placement from the .props file is unaffected, so runtime behavior is unchanged.

This fix only applies to SDK-style projects using PackageReference. Old-style packages.config projects do not process runtimes/ assets automatically and have no duplicate in the first place, so the target is a no-op for them.

Summary by CodeRabbit

• Bug Fixes

  • Closed two backlog issues (assembly version reporting and duplicate native DLL copying).

• Chores

  • Updated NuGet packaging to include additional build targets and prevent certain native runtime files from being copied to the output root for affected frameworks.

• Documentation

  • Added release process and repository/Copilot guidance; added a pointer in contributor guidance.

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---

📝 Walkthrough

Walkthrough

Adds conditional MSBuild .targets that remove package native assets from RuntimeCopyLocalItems for .NET Framework, packages those targets into NuGet builds for multiple TFMs, updates release/contributor documentation, and marks issues #1704 and #1765 resolved in the backlog.

Changes

Native DLL Copy Prevention

Layer / File(s)	Summary
MSBuild targets for native asset removal nuget/OpenCvSharp4.runtime.win.targets, nuget/OpenCvSharp4.runtime.win.slim.targets	Two new .targets files define conditional targets that execute after ResolvePackageAssets for .NET Framework (net4*/v4*) and remove package native assets from RuntimeCopyLocalItems to avoid root-level duplication.
NuGet package configuration for targets files nuget/OpenCvSharp4.runtime.win.csproj, nuget/OpenCvSharp4.runtime.win.slim.csproj	Both NuGet project files are updated to include the new .targets files under build/netstandard, build/netcoreapp, and build/net8.0, ensuring the targets are available to package consumers.
Release process and contributor guidance docs/release-process.md, .github/copilot-instructions.md, CLAUDE.md	Adds a release-process document describing versioning and CI release steps, Copilot contributor instructions covering repo structure and native DLL loading, and a pointer in CLAUDE.md.
Issue backlog update docs/issue-backlog.md	Checklist entries for issues #1704 and #1765 were toggled from unchecked to checked.

Sequence Diagram(s)

sequenceDiagram
  participant ResolvePackageAssets
  participant OpenCvSharp4RuntimeWin_RemoveRootNativeAssets
  participant OpenCvSharp4RuntimeWinSlim_RemoveRootNativeAssets
  participant RuntimeCopyLocalItems

  ResolvePackageAssets->>OpenCvSharp4RuntimeWin_RemoveRootNativeAssets: AfterTargets invoke (net4*/v4*)
  ResolvePackageAssets->>OpenCvSharp4RuntimeWinSlim_RemoveRootNativeAssets: AfterTargets invoke (net4*/v4*)
  OpenCvSharp4RuntimeWin_RemoveRootNativeAssets->>RuntimeCopyLocalItems: remove OpenCvSharp4.runtime.win entries
  OpenCvSharp4RuntimeWinSlim_RemoveRootNativeAssets->>RuntimeCopyLocalItems: remove OpenCvSharp4.runtime.win.slim entries

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Estimated Code Review Effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• shimat/opencvsharp#1816: Related to Windows slim runtime packaging/workflow and the slim package behavior that this PR modifies.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Out of Scope Changes check	⚠️ Warning	Most changes (core fixes) are in-scope. However, documentation additions (.github/copilot-instructions.md, CLAUDE.md, docs/release-process.md, docs/issue-backlog.md) are beyond the scope of fixing issue #1765 and appear to be preparatory or auxiliary additions.	Remove or separate documentation-only changes (copilot instructions, release process docs, backlog updates) into a dedicated PR focused on documentation; keep this PR focused on the technical fix for #1765.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change—fixing duplicate native DLLs in net4x output by adding .targets files to suppress redundant NuGet copies.
Linked Issues check	✅ Passed	The PR fully addresses issue #1765 by adding .targets files that prevent duplicate native DLL copies to the output root for net4x SDK-style projects using PackageReference.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@docs/issue-backlog.md`:
- Line 22: Update the resolved checklist entry that currently references "`#1704`"
to the correct issue number "`#1765`" (the duplicate native DLLs fix) in the
docs/issue-backlog.md checklist item that reads "### [x] `#1704` — Assembly
version reported as `0.0.0.0`"; if you intentionally meant to mark `#1704` as
resolved, replace the checklist text to explain why `#1704` is closed by this PR
instead of changing the issue number.

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📒 Files selected for processing (5)

• docs/issue-backlog.md
• nuget/OpenCvSharp4.runtime.win.csproj
• nuget/OpenCvSharp4.runtime.win.slim.csproj
• nuget/OpenCvSharp4.runtime.win.slim.targets
• nuget/OpenCvSharp4.runtime.win.targets

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Actionable comments posted: 1

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⚠️ Outside diff range comments (1)

docs/release-process.md (1)

1-52: ⚠️ Potential issue | 🟠 Major

Fix UTF-8 with BOM encoding for docs/release-process.md

• docs/release-process.md is missing the UTF-8 BOM (file starts with 23 20 52 = # R), so it violates the UTF-8 BOM requirement for .md files.
• Re-save it as UTF-8 with BOM:

$enc = New-Object System.Text.UTF8Encoding $true
$content = [System.IO.File]::ReadAllText("docs\release-process.md", [System.Text.Encoding]::UTF8)
[System.IO.File]::WriteAllText("docs\release-process.md", $content, $enc)

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@docs/release-process.md` around lines 1 - 52, docs/release-process.md is
missing the UTF‑8 BOM; re-save that file with UTF‑8 BOM encoding so it meets the
.md BOM requirement (e.g. use the provided PowerShell snippet that creates a
UTF8Encoding(true) and writes the file back, or re-save via your editor/IDE with
“UTF-8 with BOM”); ensure the file start bytes include the BOM (EF BB BF) before
the existing content.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@CLAUDE.md`:
- Line 1: CLAUDE.md currently lacks the UTF‑8 BOM (it starts with the bytes for
"See"), so re-save the file using UTF‑8 with BOM encoding; open CLAUDE.md and
change the file encoding to "UTF-8 with BOM" (or run a script that reads the
file as UTF‑8 and writes it back using an UTF8Encoding instance with
emitBOM=true) so the file begins with EF BB BF while preserving the existing
content.

---

Outside diff comments:
In `@docs/release-process.md`:
- Around line 1-52: docs/release-process.md is missing the UTF‑8 BOM; re-save
that file with UTF‑8 BOM encoding so it meets the .md BOM requirement (e.g. use
the provided PowerShell snippet that creates a UTF8Encoding(true) and writes the
file back, or re-save via your editor/IDE with “UTF-8 with BOM”); ensure the
file start bytes include the BOM (EF BB BF) before the existing content.

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📥 Commits

Reviewing files that changed from the base of the PR and between a5685e7 and dbed22b.

📒 Files selected for processing (8)

• .github/copilot-instructions.md
• CLAUDE.md
• docs/issue-backlog.md
• docs/release-process.md
• nuget/OpenCvSharp4.runtime.win.csproj
• nuget/OpenCvSharp4.runtime.win.slim.csproj
• nuget/OpenCvSharp4.runtime.win.slim.targets
• nuget/OpenCvSharp4.runtime.win.targets

🚧 Files skipped from review as they are similar to previous changes (5)

• docs/issue-backlog.md
• nuget/OpenCvSharp4.runtime.win.slim.csproj
• nuget/OpenCvSharp4.runtime.win.slim.targets
• nuget/OpenCvSharp4.runtime.win.csproj
• nuget/OpenCvSharp4.runtime.win.targets

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