Setup Dev and Contributing Docs

Scaffold two complementary artifacts for a repo:

1. DEVELOPMENT.md (repo root, single file) — the development spec: how to write code in this repo. Modeled on the internal-fork AGENTS.md → DEVELOPMENT.md pattern: one-line principle, branch/remote model, internal-change markers and isolation, upstream sync, design records, versioning, code-style and domain guards.
2. docs/contributing/ (four pages) — the contributing docs: how to get a change reviewed and merged. Modeled on NVIDIA NeMo Relay's contribute structure: index with "Start Here When" routing, Development Setup, Workflow and Reviews, Testing and Documentation.

Read the seed templates in templates/ — they embody both patterns; don't re-derive.

Content boundary (decided at design time — don't re-ask)

Split by when it's used: commands and gates a contributor runs at submit time → docs/contributing/; principles and guards a developer applies while writing code → DEVELOPMENT.md.

• Toolchain/env setup, pre-commit/lint commands, test thresholds, MR/PR flow, review rules → contributing
• Branch/remote model, commit-prefix markers, anchor comments, upstream sync, design records, versioning, code-style and domain guards → development
• The [<org>] commit prefix belongs in DEVELOPMENT.md (it's a sync-cost marker tied to anchor comments); contributing's commit-conventions section links to it.

Conditionality