docs: restructure agent and contributor documentation (plan 427, PR 1)

.agents/README.md

@@ -0,0 +1,25 @@
+# .agents/
+
+This is the tool-agnostic home for shared agent infrastructure used in **developing** DataDesigner.
+
+## Structure
+
+```
+.agents/
+├── skills/       # Development skills (commit, create-pr, review-code, etc.)
+├── agents/       # Sub-agent persona definitions (docs-searcher, github-searcher)
+└── README.md     # This file
+```
+
+## Compatibility
+
+Tool-specific directories symlink back here so each harness resolves skills from the same source:
+
+- `.claude/skills` → `.agents/skills`
+- `.claude/agents` → `.agents/agents`
+
+## Scope
+
+All skills and agents in this directory are for **contributors developing DataDesigner** — not for end users building datasets.
+
+The usage skill for building datasets with DataDesigner lives separately at [`skills/data-designer/`](../skills/data-designer/). For product documentation, see the [docs site](https://nvidia-nemo.github.io/DataDesigner/).

.claude/skills/review-code/SKILL.md → .agents/skills/review-code/SKILL.md

@@ -88,16 +88,13 @@ Where `<base>` is `main` unless overridden in arguments.
 
 ## Step 2: Load Project Guidelines
 
-Read `AGENTS.md` at the repository root to load the project's coding standards, design principles, and conventions. This is the authoritative source for:
+Read the following files at the repository root to load the project's standards and conventions:
 
-- Code style rules (formatting, naming, imports, type annotations)
-- Design principles (DRY, KISS, YAGNI, SOLID)
-- Testing patterns and expectations
-- Architecture and layering conventions
-- Common pitfalls to watch for
-- Lazy loading and `TYPE_CHECKING` patterns
+- **`AGENTS.md`** — architecture, layering, core design principles, structural invariants
+- **`STYLEGUIDE.md`** — code style rules (formatting, naming, imports, type annotations), design principles (DRY, KISS, YAGNI, SOLID), common pitfalls, lazy loading and `TYPE_CHECKING` patterns
+- **`DEVELOPMENT.md`** — testing patterns and expectations
 
-Use these guidelines as the baseline for the entire review. Any project-specific rules in `AGENTS.md` take precedence over general best practices.
+Use these guidelines as the baseline for the entire review. Project-specific rules take precedence over general best practices.
 
 ## Step 3: Understand the Scope
 
@@ -163,9 +160,9 @@ Final pass focused on **project conventions and test quality for new/modified co
 - Are mocks/stubs used appropriately (at boundaries, not deep internals)?
 - Do new test names clearly describe what they verify?
 
-**Project Standards (from AGENTS.md) — apply to new/modified code only:**
+**Project Standards (from AGENTS.md and STYLEGUIDE.md) — apply to new/modified code only:**
 
-Verify the items below on lines introduced or changed by this branch. Refer to the full `AGENTS.md` loaded in Step 2 for details and examples.
+Verify the items below on lines introduced or changed by this branch. Refer to `AGENTS.md` and `STYLEGUIDE.md` loaded in Step 2 for details and examples.
 
 - License headers: if present, they should be correct (wrong year or format → suggest `make update-license-headers`; don't treat as critical if CI enforces this)
 - `from __future__ import annotations` in new files

.claude/agents

@@ -0,0 +1 @@
+../.agents/agents

.claude/skills

@@ -0,0 +1 @@
+../.agents/skills