Added AI instructions for new encodings

Author: dhondta

.github/copilot-instructions.md

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+# Copilot Instructions — Enhancements Only
+
+## Scope
+This repository focuses on **adding new encoding/decoding schemes only**.
+
+Copilot MUST:
+- Propose **new codecs only**
+- Avoid refactoring unrelated code
+- Avoid dependency changes unless strictly required for the codec
+- Avoid stylistic or formatting changes
+
+## Context
+This project extends Python's codecs with many encoding/decoding schemes and CLI tools.
+It already includes a wide variety of bases, ciphers, compression, and niche encodings.
+
+## Enhancement Guidelines
+
+When adding a new encoding:
+1. Check if it already exists in the project
+2. Follow the existing codec structure and naming conventions
+3. Provide:
+   - `encode()` implementation
+   - `decode()` implementation
+   - Registration into the codec registry
+4. Ensure CLI compatibility (if applicable)
+
+## Implementation Constraints
+
+- Pure Python preferred
+- No heavy dependencies
+- Deterministic transformations only
+- Reversible encoding required unless explicitly documented
+
+## Testing
+
+Every new codec MUST include:
+- Unit tests (encode/decode roundtrip)
+- Edge cases (empty input, binary data if applicable)
+
+## Documentation
+
+Each codec must include:
+- Short description
+- Reference (standard, RFC, or algorithm source)
+- Example usage
+
+## Output Format (IMPORTANT)
+
+When asked to add a codec, Copilot should:
+1. Briefly justify the encoding (1–2 lines)
+2. Provide full implementation
+3. Provide tests
+4. Provide documentation snippet
+
+## Explicit Non-Goals
+
+- No refactoring
+- No performance optimization passes
+- No linting-only changes
+- No CI/CD changes

.github/prompts/add_codec.prompt.md

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+Add a new encoding scheme to this repository.
+
+Constraints:
+- Follow copilot-instructions.md strictly
+- Do not modify unrelated code
+- Use existing codec patterns
+
+Task:
+Add encoding: {{ENCODING_NAME}}
+
+Requirements:
+- Implement according to ADDING_CODECS.md guideline
+- Add tests if needed (if `__examples__` cannot be consistently defined)
+- Add minimal documentation (in the relevant category page under `docs/pages`)
+
+Reference:
+{{LINK_OR_DESCRIPTION}}

.github/pull_request_template.md

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+## Type
+- [ ] New encoding (required)
+
+## Checklist
+- [ ] No unrelated changes
+- [ ] Codec is new (not already implemented)
+- [ ] Tests included (if cannot be automated with `tests/test_generated`)
+- [ ] Documentation (included in the right page in `docs/pages/enc`)
+
+## Description
+Explain the encoding and its source.

docs/ADDING_CODECS.md

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+# Adding a Codec
+
+1. Categorize accordingly ; categories are the folder names in `src/codext` (further folder references are relative to this). When a category cannot be put in one of these folders, it shall be put by default in `others`.
+
+2. Add the `.py` file in the relevant category folder, named with the short name of the new codec.
+
+3. Respect the typical structure of a codec's `.py` file according to the following template (double-bracketed enclosures indicate codec parameters, double-arrowed enclosures indicate instructions that may refer to further steps of this guideline):
+
+    ```python
+    # -*- coding: UTF-8 -*-
+    """{{codec_long_name}} Codec - {{codec_short_name}} content encoding.
+
+    {{codec_description}}
+
+    This codec:
+    - en/decodes strings from str to str
+    - en/decodes strings from bytes to bytes
+    - decodes file content to str (read)
+    - encodes file content from str to bytes (write)
+
+    Reference: {{codec_source_hyperlink}}
+    """
+    from ..__common__ import *
+
+
+    __examples__ = {<<dictionary of examples with, as keys, a special format detailed hereafter and, as values, a dictionary mapping source to destination values (see 7.)>>}
+    <<optional list of valid codec names to be used with the guessing mode (see 8.), in format "__guess__ = [...]">>]
+
+
+    <<constants here, including ENCMAP if the codec is a simple mapping (see 6.)>>
+    <<functions here, if the codec requires some additional logic, i.e. when it is not a mapping (see 6.)>>
+
+
+    <<put the right add function (see 4.) here with its relevant parameters (see 5.)>>
+    ```
+
+4. Choose the right add function
+
+    If the codec is a simple mapping, use the `add_map` function.
+    
+    Examples: `languages/braille`, `languages/morse`, `languages/southpark`
+
+    In some cases, an algorithm can even be equivalent to one or a number of mappings and can then be defined as a dynamic generation of `ENCMAP`.
+    
+    Examples: `stegano/resistor`, `crypto/barbie`
+    
+    When the codec is more complex than a mapping, use the `add` function.
+
+5. Configure the add function
+
+    Refer to the relevant function signature in `__common__.py`.
+
+6. Write the codec logic
+
+    If the codec is a mapping, at least `ENC_MAP` should be defined and refered in the parameters of the `add_map` function.
+    
+    Examples: `stegano/rick`, `stegano/klopf`
+    
+    If the codec is not a mapping, the logic can be written in the following order: the encoding function first, then the decoding function.
+    
+    Examples: `stegano/whitespace`, `crypto/railfence`
+
+7. Write some examples
+
+    Examples are used during the automated test generation. They should then be carefully written to also cover some edge cases. A set of 3-8 examples is generally a must.
+
+8. Specify the names to be used with the guessing mode
+
+    The `__guess__` list of codec names is used to limit the possibilities in the tree search from the guessing mode. Especially when the codec is dynamic and may have a large (or even infinite) number of dynamic names, it is necessary to set a limited number, generally maximum 16 as a best practice. This list, when relevant, shall be used with due care.