audit fixes, repo restructure, and documentation

Soundness and performance audit (17 fixes):
- See AUDIT.md for full details and @claude comments in code

Repo restructure:
- Inline json-ptr and json-patch submodules as regular directories
- Remove cbor submodule, replace serde_cbor with ciborium
- Rename patch-db/ -> core/, patch-db-macro/ -> macro/,
  patch-db-macro-internals/ -> macro-internals/, patch-db-util/ -> util/
- Purge upstream CI/CD, bench, and release cruft from json-patch
- Remove .gitmodules

Test fixes:
- Fix proptest doesnt_crash (unique file paths, proper close/cleanup)
- Add PatchDb::close() for clean teardown

Documentation:
- Add README.md, ARCHITECTURE.md, CONTRIBUTING.md, CLAUDE.md, AUDIT.md
- Add TSDocs to TypeScript client exports

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

CONTRIBUTING.md

@@ -0,0 +1,87 @@
+# Contributing
+
+## Prerequisites
+
+- **Rust** — stable toolchain (edition 2018+)
+- **Node.js** — v16+ with npm
+
+## Building
+
+### Rust
+
+```bash
+cargo build                        # Build all crates
+cargo build --features debug       # Build with tracing support
+```
+
+### TypeScript client
+
+```bash
+cd client
+npm install
+npm run build    # Compiles to dist/
+npm run check    # Type-check without emitting
+```
+
+## Testing
+
+### Rust
+
+```bash
+cargo test                 # Run all tests
+cargo test -p patch-db     # Core crate only
+cargo test -p json-ptr     # JSON Pointer crate only
+cargo test -p json-patch   # JSON Patch crate only
+```
+
+The core crate uses `proptest` for property-based testing.
+
+### TypeScript
+
+The client uses pre-commit hooks (husky) for linting:
+
+```bash
+cd client
+npx prettier --check "**/*.{js,ts,html,md,less,json}"
+npx tslint --project .
+```
+
+## CLI utility
+
+`patch-db-util` provides commands for inspecting and restoring database files:
+
+```bash
+# Dump database state as JSON
+cargo run -p patch-db-util -- dump path/to/my.db
+
+# Restore database from JSON on stdin
+echo '{"count": 42}' | cargo run -p patch-db-util -- from-dump path/to/my.db
+```
+
+## Code style
+
+### Rust
+
+- Follow standard `rustfmt` conventions
+- Use `thiserror` for error types
+- Async functions use `tokio`
+
+### TypeScript
+
+- Prettier for formatting (runs via pre-commit hook)
+- TSLint for linting (runs via pre-commit hook)
+- RxJS conventions: suffix observables with `$`
+
+## Making changes
+
+1. **Check [ARCHITECTURE.md](ARCHITECTURE.md)** to understand which crate(s) your change touches
+2. **Follow existing patterns** — look at neighboring code before inventing new abstractions
+3. **Cross-layer changes** (Rust types that affect the TS client) require updating both sides to keep the wire format compatible:
+   - `Revision` and `Dump` types must match between `core/src/patch.rs` and `client/lib/types.ts`
+   - Patch operations (add/remove/replace) must match between `json-patch/` and `client/lib/json-patch-lib.ts`
+4. **Run tests** before submitting
+
+## Commit conventions
+
+- Use imperative mood in commit messages ("add feature", not "added feature")
+- Keep commits focused — one logical change per commit