Add initial basic GitHub Copilot instructions (#137754)

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>
Co-authored-by: Joost Lekkerkerker <joostlek@outlook.com>

.github/copilot-instructions.md

@@ -0,0 +1,100 @@
+# Instructions for GitHub Copilot
+
+This repository holds the core of Home Assistant, a Python 3 based home
+automation application.
+
+- Python code must be compatible with Python 3.13
+- Use the newest Python language features if possible:
+  - Pattern matching
+  - Type hints
+  - f-strings for string formatting over `%` or `.format()`
+  - Dataclasses
+  - Walrus operator
+- Code quality tools:
+  - Formatting: Ruff
+  - Linting: PyLint and Ruff
+  - Type checking: MyPy
+  - Testing: pytest with plain functions and fixtures
+- Inline code documentation:
+  - File headers should be short and concise:
+    ```python
+    """Integration for Peblar EV chargers."""
+    ```
+  - Every method and function needs a docstring:
+    ```python
+    async def async_setup_entry(hass: HomeAssistant, entry: PeblarConfigEntry) -> bool:
+        """Set up Peblar from a config entry."""
+        ...
+    ```
+- All code and comments and other text are written in American English
+- Follow existing code style patterns as much as possible
+- Core locations:
+  - Shared constants: `homeassistant/const.py`, use them instead of hardcoding
+    strings or creating duplicate integration constants.
+  - Integration files:
+    - Constants: `homeassistant/components/{domain}/const.py`
+    - Models: `homeassistant/components/{domain}/models.py`
+    - Coordinator: `homeassistant/components/{domain}/coordinator.py`
+    - Config flow: `homeassistant/components/{domain}/config_flow.py`
+    - Platform code: `homeassistant/components/{domain}/{platform}.py`
+- All external I/O operations must be async
+- Async patterns:
+  - Avoid sleeping in loops
+  - Avoid awaiting in loops, gather instead
+  - No blocking calls
+- Polling:
+  - Follow update coordinator pattern, when possible
+  - Polling interval may not be configurable by the user
+  - For local network polling, the minimum interval is 5 seconds
+  - For cloud polling, the minimum interval is 60 seconds
+- Error handling:
+  - Use specific exceptions from `homeassistant.exceptions`
+  - Setup failures:
+    - Temporary: Raise `ConfigEntryNotReady`
+    - Permanent: Use `ConfigEntryError`
+- Logging:
+  - Message format:
+    - No periods at end
+    - No integration names or domains (added automatically)
+    - No sensitive data (keys, tokens, passwords), even when those are incorrect.
+  - Be very restrictive on the use of logging info messages, use debug for
+    anything which is not targeting the user.
+  - Use lazy logging (no f-strings):
+    ```python
+    _LOGGER.debug("This is a log message with %s", variable)
+    ```
+- Entities:
+  - Ensure unique IDs for state persistence:
+    - Unique IDs should not contain values that are subject to user or network change.
+    - An ID needs to be unique per platform, not per integration.
+    - The ID does not have to contain the integration domain or platform.
+    - Acceptable examples:
+      - Serial number of a device
+      - MAC address of a device formatted using `homeassistant.helpers.device_registry.format_mac`
+        Do not obtain the MAC address through arp cache of local network access,
+        only use the MAC address provided by discovery or the device itself.
+      - Unique identifier that is physically printed on the device or burned into an EEPROM
+    - Not acceptable examples:
+      - IP Address
+      - Device name
+      - Hostname
+      - URL
+      - Email address
+      - Username
+    - For entities that are setup by a config entry, the config entry ID
+      can be used as a last resort if no other Unique ID is available.
+      For example: `f"{entry.entry_id}-battery"`
+  - If the state value is unknown, use `None`
+  - Do not use the `unavailable` string as a state value,
+    implement the `available()` property method instead
+  - Do not use the `unknown` string as a state value, use `None` instead
+- Extra entity state attributes:
+  - The keys of all state attributes should always be present
+  - If the value is unknown, use `None`
+  - Provide descriptive state attributes
+- Testing:
+  - Test location: `tests/components/{domain}/`
+  - Use pytest fixtures from `tests.common`
+  - Mock external dependencies
+  - Use snapshots for complex data
+  - Follow existing test patterns