docs: add AI tool instruction files

.devcontainer/devcontainer.json

@@ -1,11 +1,11 @@
 {
     "name": "ShinyPDF Tests",
     "image": "mcr.microsoft.com/dotnet/sdk:10.0",
-    "postCreateCommand": "apt-get update && apt-get install -y libfontconfig1 libfreetype6 libpng16-16t64 libharfbuzz0b libjpeg-turbo8 libgif7 libwebp7 && dotnet restore src/ShinyPDF.sln",
+    "postCreateCommand": "apt-get update && apt-get install -y libfontconfig1 libfreetype6 libpng16-16t64 libharfbuzz0b libjpeg-turbo8 libgif7 libwebp7 && dotnet restore src/ShinyPDF.slnx",
     "customizations": {
         "vscode": {
             "settings": {
-                "dotnet.defaultSolution": "src/ShinyPDF.sln"
+                "dotnet.defaultSolution": "src/ShinyPDF.slnx"
             },
             "extensions": [
                 "ms-dotnettools.csharp",

.github/copilot-instructions.md

@@ -0,0 +1,9 @@
+# Copilot instructions
+
+Follow [AGENTS.md](../AGENTS.md) in the repository root. It holds the project rules, commands, and workflow for all AI tools.
+
+When reviewing pull requests, check in particular:
+
+- Changes to the public API (`ShinyPDF.Fluent`, public types) that break consumers need a `BREAKING CHANGE:` commit footer.
+- SkiaSharp, HarfBuzzSharp and their `NativeAssets.*` packages stay on matching versions.
+- Tests use NUnit `Assert.That`.

.vscode/settings.json

@@ -1,3 +1,3 @@
 {
-	"dotnet.defaultSolution": "src/ShinyPDF.sln",
+	"dotnet.defaultSolution": "src/ShinyPDF.slnx",
 }

AGENTS.md

@@ -0,0 +1,41 @@
+# ShinyPDF - .NET library for PDF generation with a C# Fluent API
+
+The single orientation file for any AI agent (Claude Code, Copilot, Codex, ...) and any human working in this repo. Keep it current.
+
+## Project
+
+- Status: active. Open-source library, published to NuGet as `ShinyPDF`. Fork of the last MIT-licensed version of QuestPDF.
+- Stack: C# / .NET 10 (SDK pinned in `src/global.json`), SkiaSharp + HarfBuzzSharp for rendering, NUnit for tests.
+- Layout: `src/ShinyPDF` (library: `Fluent` = public API, `Elements`, `Drawing`, `Infrastructure`, `Helpers`), `src/ShinyPDF.UnitTests` (fast tests with an operation-recording test engine), `src/ShinyPDF.Examples` (NUnit tests that render real PDFs/images).
+
+## Key rules
+
+- Never commit `.env`, `*.tfvars`, or `.claude/settings.local.json`.
+- The public API (`ShinyPDF.Fluent`, public types) is used by consumers: breaking changes need a `BREAKING CHANGE:` commit footer (major release).
+- SkiaSharp, HarfBuzzSharp and their `NativeAssets.*` packages must stay on matching versions, including the Linux ones in `Directory.Build.props`.
+- Native asset references in `Directory.Build.props` keep `PrivateAssets="all"` so they never become package dependencies.
+- The `Grid` element's `[Obsolete]` marker is inherited from the QuestPDF base, not a ShinyPDF decision; it may be reintroduced. Do not remove `Grid` or migrate existing usages unprompted; its CS0618 warnings are expected.
+- Use NUnit `Assert.That` in tests (no FluentAssertions).
+
+## Commands
+
+```bash
+dotnet build src/ShinyPDF.slnx                                    # build all projects
+dotnet test src/ShinyPDF.UnitTests/ShinyPDF.UnitTests.csproj      # unit tests (seconds, what CI runs)
+dotnet test src/ShinyPDF.Examples/ShinyPDF.Examples.csproj        # example renders (~8 min, writes PDFs/PNGs to bin/)
+dotnet pack src/ShinyPDF/ShinyPDF.csproj -c Release -o out        # local NuGet package
+```
+
+Example tests marked `.ShowResults()` try to open the generated file in a viewer; run them only when rendering changed.
+On Linux (or with `SHINYPDF_DEVCONTAINER=true`) the Linux native assets are added automatically.
+
+## Workflow
+
+- GitHub: `LM-Development/ShinyPDF`, use `gh` for issues and PRs. Branch from `main`, open a PR, CI (`pull-request.yaml`) builds and runs the unit tests.
+- Commits follow Conventional Commits. Every push to `main` runs `release.yaml`: `feat:` / `fix:` / `BREAKING CHANGE` create a GitHub release and publish to NuGet; `chore:`, `test:`, `docs:` release nothing.
+- Merge PRs with a merge commit, not squash, so commit types and footers reach `main` unchanged.
+- Published NuGet versions cannot be deleted, only unlisted: check the commit type before merging.
+
+## Current focus
+
+Open issues: user documentation (#9, #22), more underline options (#11), template designer app (#12).

CLAUDE.md

@@ -0,0 +1,10 @@
+# ShinyPDF
+
+Read [AGENTS.md](AGENTS.md) first. All project rules, commands, and workflow live there; this file holds only what is Claude-specific.
+
+## Claude-specific rules
+
+- No em-dashes in any generated text, code comments, or commit messages.
+- This repo is on GitHub: use `gh`, not `az repos` / `az boards`.
+- Before claiming done or fixed: verify the actual result (tests run, package packed, release visible), or say "UNVERIFIED". A green build is not verification.
+- On Windows, PowerShell 5.1 writes UTF-8 with BOM by default; preserve the existing encoding of files you edit.