docs: add AGENTS.md with core commands

AGENTS.md

@@ -0,0 +1,37 @@
+# Agent Guidance
+
+## Core Commands
+
+```bash
+# Build
+cargo build
+
+# Format check
+cargo fmt --check
+
+# Lint
+cargo clippy -- -D warnings
+
+# Type check
+cargo check
+
+# Run tests
+cargo test
+
+# Check vendored artifacts (openapi.json + docs/HELP.md) are up to date
+cargo xtask check
+
+# Regenerate docs/HELP.md from current CLI definitions
+cargo xtask generate-help > docs/HELP.md
+
+# Regenerate openapi.json from upstream API
+cargo xtask generate-openapi
+```
+
+## CI
+
+CI runs formatting, clippy, check, tests, vendored artifact checks, and a security audit. All must pass before merge.
+
+## Lint Policy
+
+Clippy is configured with strict `pedantic`, `nursery`, and many restriction lints denied. See `[lints.clippy]` in `Cargo.toml` for the full list. Notable: `unwrap_used`, `expect_used`, `panic`, and `unsafe_code` are all denied outside of tests.