Add Claude Code setup guide for contributors

Create dev-docs/claude-code-setup.md explaining .claude/ files,
path-scoped rules, CLAUDE.local.md overrides, and how to add or
update rules. Add AI-Assisted Development section to CONTRIBUTING.md.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: cderv

CONTRIBUTING.md

@@ -31,3 +31,7 @@ Pull requests are very welcome! Here's how to contribute via PR:
 3.  Submit the [pull request](https://help.github.com/articles/using-pull-requests). It is ok to submit as draft if your are still working on it but would like some feedback from us. It is always good to share in the open that you are working on it.
 
 We'll try to be as responsive as possible in reviewing and accepting pull requests.
+
+## AI-Assisted Development
+
+This repository includes shared [Claude Code](https://docs.anthropic.com/en/docs/claude-code) memory files in `.claude/` that help AI assistants understand the Quarto codebase. See [dev-docs/claude-code-setup.md](dev-docs/claude-code-setup.md) for details on how these work and how to contribute to them.

dev-docs/claude-code-setup.md

@@ -0,0 +1,87 @@
+# Claude Code Setup for Quarto Contributors
+
+This project includes shared [Claude Code](https://docs.anthropic.com/en/docs/claude-code) memory files that help AI assistants understand the Quarto codebase. These files are committed to the repository so all contributors benefit from consistent AI-assisted development.
+
+## What's Included
+
+### `.claude/CLAUDE.md`
+
+Always loaded by Claude Code. Contains the project overview: architecture, setup, build commands, conventions, and key file paths.
+
+### `.claude/rules/`
+
+Path-scoped rule files that load conditionally based on what files you're working with. For example, when editing Lua filters, Claude Code automatically loads filter-specific conventions.
+
+Current rule areas:
+- `changelog.md` — Changelog entry format
+- `filters/` — Lua filter coding conventions and system overview
+- `formats/` — Format handler patterns
+- `rendering/` — Render pipeline architecture
+- `schemas/` — Zod schema patterns
+- `testing/` — Test infrastructure, smoke-all format, Playwright, anti-patterns
+- `typescript/` — Deno essentials, RAL, Cliffy commands
+- `dev-tools/` — Development commands reference
+- `llm-docs-maintenance.md` — LLM documentation staleness checking
+
+Each rule file has a `paths:` frontmatter that controls when it loads:
+
+```yaml
+---
+paths:
+  - "src/resources/filters/**"
+---
+```
+
+This means the file only loads when Claude Code is working with files matching those paths.
+
+### `llm-docs/`
+
+Architectural deep-dive documentation for AI assistants. These are NOT auto-loaded — they're read on demand when Claude Code needs detailed understanding of a subsystem. Topics include template systems, error messages, testing patterns, and Lua API reference.
+
+Each llm-doc has staleness metadata in its frontmatter so Claude Code can check if the documented code has changed since the analysis was done.
+
+## Personal Overrides
+
+Create `CLAUDE.local.md` at the repository root for personal overrides. This file is gitignored and won't be committed. Use it for:
+
+- Preferred shell syntax or platform-specific notes
+- Personal workflow customizations
+- References to personal tools or configurations
+
+Claude Code loads `CLAUDE.local.md` alongside the project `CLAUDE.md`.
+
+## Adding or Updating Rules
+
+### New rule file
+
+1. Create `.claude/rules/<area>/rule-name.md`
+2. Add `paths:` frontmatter listing glob patterns relative to the repo root (e.g., `"src/resources/filters/**"`)
+3. Keep rules focused and concise (50-250 lines is typical)
+
+### Update existing rule
+
+Edit the relevant file in `.claude/rules/`. The path scoping ensures changes only affect sessions working with matching files.
+
+### New llm-doc
+
+1. Create `llm-docs/topic-name.md`
+2. Add staleness frontmatter (`main_commit`, `analyzed_date`, `key_files`)
+3. Reference from relevant rule files if helpful
+
+## What's NOT Committed
+
+The `.gitignore` excludes personal Claude Code files:
+
+```
+CLAUDE.local.md           # Personal overrides
+.claude/commands/         # Personal slash commands
+.claude/docs/             # Personal documentation
+.claude/settings.local.json  # Local settings
+```
+
+These stay personal to each developer.
+
+## Further Reading
+
+- [Claude Code documentation](https://docs.anthropic.com/en/docs/claude-code)
+- [Memory files reference](https://docs.anthropic.com/en/docs/claude-code/memory)