Lower Python requirement to 3.9; CI matrix adds 3.9

The codebase already uses 'from __future__ import annotations' everywhere,
so PEP 604 union syntax (str | None) and similar 3.10+ annotations are
strings at runtime and don't break on 3.9. Tests have been running on 3.9
locally throughout development with no failures.

Lowering requires-python eliminates the '--ignore-requires-python' workaround
for users on macOS-default Python 3.9 (still common despite 3.10's release).

Changes:
- pyproject.toml: requires-python = '>=3.9'
- .github/workflows/test.yml: matrix adds 3.9 alongside 3.10/3.11/3.12
- README, README.ru, QUICKSTART: drop the workaround note, state 'Python 3.9+'

Author: sedelev

.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.10", "3.11", "3.12"]
+        python-version: ["3.9", "3.10", "3.11", "3.12"]
 
     steps:
       - uses: actions/checkout@v4

QUICKSTART.md

@@ -19,9 +19,7 @@ python3 --version   # macOS / Linux
 python --version    # Windows (WSL)
 ```
 
-You should see **Python 3.10 or higher**.
-
-> **Note:** If you see Python 3.9, you can still install with `pip install -e . --ignore-requires-python`. The code works on 3.9, but official support and CI target 3.10+.
+You should see **Python 3.9 or higher**. (CI tests 3.9, 3.10, 3.11, 3.12.)
 
 If Python is not installed:
 - **macOS:** install from [python.org/downloads](https://www.python.org/downloads/) or run `brew install python`
@@ -197,7 +195,7 @@ pip install -e .
 | Empty `.md` files | No messages in session | Check `messageCount` in `list` output |
 | Corrupt JSONL warning | Malformed `.jsonl` lines | Normal — tool skips bad lines, continues |
 | Windows: command not found | Native CMD/PowerShell | Use **WSL2** — native Windows not tested |
-| Python version error | Running Python 3.9 | `pip install -e . --ignore-requires-python` or upgrade to 3.10+ |
+| Python version error | Running Python <3.9 | Upgrade to Python 3.9 or newer |
 
 ---
 

README.md

@@ -64,14 +64,12 @@ New users: see [QUICKSTART.md](./QUICKSTART.md) for the full step-by-step guide
 
 ## Install
 
-Requires **Python 3.10+** (CI tests 3.10, 3.11, 3.12).
+Requires **Python 3.9+** (CI tests 3.9, 3.10, 3.11, 3.12).
 
 ```bash
 pip install -e .
 ```
 
-> **Note:** If you only have Python 3.9, you can install with `pip install -e . --ignore-requires-python`. The code uses `from __future__ import annotations` and works on 3.9, but official support is 3.10+.
-
 ---
 
 ## Usage
@@ -199,7 +197,7 @@ pip install -e ".[dev]"
 pytest -v --cov=claude_backup
 ```
 
-CI runs on Python 3.10, 3.11, and 3.12 — see [.github/workflows/test.yml](.github/workflows/test.yml).
+CI runs on Python 3.9, 3.10, 3.11, and 3.12 — see [.github/workflows/test.yml](.github/workflows/test.yml).
 
 **Test coverage: 91%** (68/68 tests passing) — covers the real Claude Code format, the legacy spec format, edge cases (empty/corrupt JSONL, unicode, missing index), `--mode` selection (both / minimal / full), and CLI integration.
 

README.ru.md

@@ -64,14 +64,12 @@ claude-backup export-all --output ~/claude-backups/
 
 ## Установка
 
-Требуется **Python 3.10+** (CI тестирует 3.10, 3.11, 3.12).
+Требуется **Python 3.9+** (CI тестирует 3.9, 3.10, 3.11, 3.12).
 
 ```bash
 pip install -e .
 ```
 
-> **Примечание:** Если у вас Python 3.9, установка возможна с `pip install -e . --ignore-requires-python`. Код использует `from __future__ import annotations` и работает на 3.9, но официальная поддержка — 3.10+.
-
 ---
 
 ## Использование
@@ -196,7 +194,7 @@ pip install -e ".[dev]"
 pytest -v --cov=claude_backup
 ```
 
-CI запускается на Python 3.10, 3.11 и 3.12 — см. [.github/workflows/test.yml](.github/workflows/test.yml).
+CI запускается на Python 3.9, 3.10, 3.11 и 3.12 — см. [.github/workflows/test.yml](.github/workflows/test.yml).
 
 **Покрытие тестами: 91%** (68/68 тестов проходят) — реальный формат Claude Code, legacy-формат из спеки, edge-кейсы (пустой/битый JSONL, unicode, отсутствующий индекс), выбор `--mode` (both / minimal / full), и интеграционные тесты CLI.
 

pyproject.toml

@@ -7,7 +7,7 @@ name = "claude-backup"
 version = "0.1.0"
 description = "Export Claude Code session history to Markdown"
 readme = "README.md"
-requires-python = ">=3.10"
+requires-python = ">=3.9"
 license = {text = "MIT"}
 authors = [
     {name = "parallelclaw"}