Unify documentation rules across languages and fix the Python template

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Rust/DESIGN_DOCUMENT.md

@@ -14,11 +14,17 @@
 - **PROJECT.md** — Project goals and current state
 - **CHANGELOG.md** — Version history
 
+### Documentation Organization
+
+All detailed documentation of features and systems belongs in the `docs/` folder, not in the project root.
+
+The root directory contains only the core documents: `README.md`, `AGENTS.md`, `DESIGN_DOCUMENT.md`, `PROJECT.md`, `CHANGELOG.md`.
+
 ---
 
 ## 1. Code Style
 
-- **Rust edition:** 2021
+- **Rust edition:** 2024 (requires Rust 1.85 or newer)
 - Format with **rustfmt** — run `cargo fmt` before every commit
 - Lint with **clippy** — run `cargo clippy -- -D warnings` before every commit
 - **snake_case** functions/variables/modules, **PascalCase** types/traits, **SCREAMING_SNAKE_CASE** constants
@@ -55,6 +61,7 @@ project/
 │   └── <module>/
 │       └── mod.rs
 ├── tests/                  # Integration tests
+├── docs/                   # Detailed documentation
 ├── Cargo.toml
 └── Cargo.lock              # Commit for applications, not for libraries
 ```
@@ -196,10 +203,20 @@ cross build --release --target x86_64-pc-windows-gnu
 ## 11. Documentation and Task Management
 
 - Keep `PROJECT.md` and `CHANGELOG.md` up to date when making changes
+- Document architectural changes in this file or in `docs/`
 
 ### Task notation
 
+Tasks are written as single-line comments directly in code, using the **Todo Tree** tags defined in `AGENTS.md` (`TODO`, `FIXME`, `BUG`, `HACK`, `NOTE`). `PROJECT.md` carries only cross-cutting tasks that have no single place in the code.
+
 ```rust
-// TODO: one-liner description of a task to be done
-// FIXME: one-liner description of a known bug to be fixed
+// TODO: extract this into a separate module
+// FIXME: panics on an empty slice
+// BUG: off-by-one when the buffer is exactly full
+// HACK: temporary workaround until the crate adds paging
+// NOTE: order matters here, the parser is stateful
 ```
+
+No other task format is used — **no checkboxes, no numbered lists in documentation**.
+
+If a tag already exists at a specific location in code, do not repeat it in `PROJECT.md`.