docs: define v0.1 product and architecture contract

AGENTS.md

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+# AGENTS.md
+
+## Read first
+
+- Read `PRD.md`, `CONTEXT.md`, and applicable ADRs before changing behavior.
+- Keep the Rust harness synchronous and the Ghidra worker
+  capability-sandboxed.
+- Treat JSON schemas, error codes, ordering, and exit statuses as public API.
+
+## Change rules
+
+- Add a regression test for every bug fix.
+- Never change golden files or schemas implicitly.
+- Keep the Rust operation registry, Java dispatch, schemas, and goldens in
+  exact parity.
+- Preserve strict stdout/stderr framing.
+- Preserve the worker's no-network and no-default-data-egress boundary.
+- Do not add `unsafe`, an async runtime, database, daemon, or dependency
+  without an accepted design change.
+- Do not weaken bounds, validation, sandboxing, or atomic store behavior.
+
+## Required checks
+
+- `cargo fmt --check`
+- `cargo clippy --all-targets --all-features -- -D warnings`
+- `cargo test --all-targets`
+- `cargo deny check`
+- `nix flake check`
+
+## Source control
+
+- Use Jujutsu for normal local change management.
+- Use `jj status`, `jj diff`, `jj log`, `jj describe`, and `jj new`.
+- Push Forgejo bookmarks through `jj git push`.
+- Keep changes focused and preserve unrelated user work.
+- Use direct Git commands only for interop or recovery that Jujutsu cannot
+  perform.
+- Never run `git clean -xdf`; it can delete colocated `.jj/` metadata.