## Implementation Plan

### Changes Required (6 locations across 4 files)

1. **`devplacepy/models.py`, line 256 and 262**  
   - Change both `AiModifierForm.prompt` and `AiCorrectionForm.prompt` from `Field(max_length=2000)` to `Field(max_length=20000)`.  
   - The field definition is already there; update the literal value.

2. **`devplacepy/templates/profile.html`, lines 225 and 250**  
   - Change both `<textarea maxlength="2000" ...>` to `<textarea maxlength="20000" ...>`.  
   - The `data-ai-correction-prompt` and `data-ai-modifier-prompt` textareas each get the updated attribute.

3. **`devplacepy/services/devii/ai_correction/controller.py`, line 73**  
   - Replace `str(prompt_raw).strip()[:2000]` with `str(prompt_raw).strip()[:20000]`.

4. **`devplacepy/services/devii/ai_modifier/controller.py`, line 73**  
   - Replace `str(prompt_raw).strip()[:2000]` with `str(prompt_raw).strip()[:20000]`.

No other files require changes.

### Execution Steps

1. Apply the edits above to the four files.
2. Run the project’s verification commands. Note that the Python environment may enforce PEP 668; use the following workaround:
   ```bash
   PIP_REQUIRE_VIRTUALENV=0 pip install -e '.[dev]' -q && make test-unit
   ```
3. Run the linter:
   ```bash
   pip install -q ruff && ruff check .
   ```

### Definition of Done

- [ ] All six locations (2 Pydantic fields, 2 HTML attributes, 2 controller slices) have been updated from 2000 to 20000.
- [ ] `PIP_REQUIRE_VIRTUALENV=0 pip install -e '.[dev]' -q && make test-unit` exits with code 0.
- [ ] `ruff check .` exits with code 0 (no linting errors).
- [ ] (Optional) Confirm the change by inspecting the four files for the new limit value:
  - `grep -n "max_length=20000\|maxlength=\"20000\"\|\[:20000\]" devplacepy/models.py devplacepy/templates/profile.html devplacepy/services/devii/ai_correction/controller.py devplacepy/services/devii/ai_modifier/controller.py` should show exactly 6 matches.