docs: add spec, plan, and tasks for filters task wording fix (#12)

specs/012-filters-tasks/plan.md

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+# Implementation Plan
+
+## Objective
+
+Rewrite the 4 CSS Filters lessons in `lessons/11-filters.json` so tasks describe visual outcomes instead of giving exact CSS code, and validations accept multiple valid answers.
+
+## Approach
+
+Follow the same pattern established in issue #9 (colors/box-model rewrite):
+1. Rewrite each `task` field to describe the desired visual effect
+2. Replace exact-match validations (`property_value`, `contains`) with `regex` validations that accept a range of values
+3. Update validation `message` fields to give pedagogical hints without revealing answers
+4. Keep `description`, `previewHTML`, `previewBaseCSS`, `codePrefix`, `codeSuffix`, and `solution` unchanged
+
+## File Mapping
+
+| File | Action | Description |
+|------|--------|-------------|
+| `lessons/11-filters.json` | modify | Rewrite tasks and validations for all 4 lessons |
+
+## Lesson-by-Lesson Plan
+
+### filters-1: Blur Filter
+- **Current task:** "Blur the background image using `filter: blur(4px)`."
+- **New task:** Describe frosted-glass effect, mention blur radius range (2px-8px)
+- **Validation:** `regex` matching `filter:\s*blur\((2|3|4|5|6|7|8)px\)` — accepts 2px through 8px
+- **Message:** Hint about the `filter` property and `blur()` function
+
+### filters-2: Grayscale Filter
+- **Current task:** "Make the image grayscale with `filter: grayscale(100%)`."
+- **New task:** Describe removing all color to create a black-and-white effect
+- **Validation:** `regex` matching `filter:\s*grayscale\(100%\)` — grayscale only makes sense at 100% for "fully desaturated"
+- **Message:** Hint about which filter function removes color
+
+### filters-3: Brightness Filter
+- **Current task:** "Brighten the card with `filter: brightness(120%)`."
+- **New task:** Describe making the card appear brighter/more vivid, accept range 110%-150%
+- **Validation:** `regex` matching `filter:\s*brightness\(1[1-5]0%\)` — accepts 110% through 150%
+- **Message:** Hint about the brightness function and values above 100%
+
+### filters-4: Drop Shadow
+- **Current task:** "Add a drop shadow with `filter: drop-shadow(4px 4px 8px gray)`."
+- **New task:** Describe adding a soft shadow behind the star to give it depth
+- **Validation:** `regex` matching `filter:\s*drop-shadow\(` with reasonable offset/blur values
+- **Message:** Hint about the drop-shadow filter function
+
+## Architecture Decisions
+
+- Use `regex` validation type (not `property_value`) to allow multiple acceptable values, consistent with the colors/box-model rewrite
+- Use `options: { "caseSensitive": false }` on all regex validations for consistency
+- Keep solution fields unchanged as reference answers
+
+## Risks
+
+| Risk | Mitigation |
+|------|------------|
+| Regex too permissive | Test edge cases; only accept pedagogically reasonable values |
+| Regex too restrictive | Allow generous ranges; err on the side of accepting creative answers |
+| Breaking existing progress | localStorage keys are based on lesson IDs which are unchanged |
+
+## Testing Strategy
+
+- Run existing test suite (`npm test`) to verify no regressions
+- Validate JSON file against schema
+- Manual review of regex patterns for correctness

specs/012-filters-tasks/spec.md

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+# fix: rewrite CSS Filters tasks to describe visual outcomes instead of exact code
+
+**Issue:** [#12](https://git.librete.ch/libretech/code-crispies/issues/12)
+**Repository:** libretech/code-crispies
+**Author:** libretech
+**State:** open
+**Labels:** none
+
+## Problem
+
+Pedagogy audit: the Filters module has a 100% copy-paste score. Every exercise gives the exact CSS declaration in the task text, so students can complete lessons without understanding the concepts.
+
+## Requirements
+
+- Rewrite ONLY the filters module (`lessons/11-filters.json`) task descriptions to describe the desired visual effect instead of the exact code
+- Accept multiple valid values in validations (e.g., accept blur values between 2px and 8px instead of only 4px)
+- Do NOT change any other module
+
+## Example
+
+- **Before:** "Add `filter: blur(4px)`"
+- **After:** "Blur the background image to create a frosted-glass effect. Use a blur radius between 2px and 8px."
+
+## Acceptance Criteria
+
+1. All 4 filter lesson tasks describe visual outcomes, not exact CSS
+2. Validations accept a range of valid values using regex patterns
+3. Validation messages provide pedagogical hints without revealing answers
+4. No changes to any file outside `lessons/11-filters.json`
+5. Existing tests continue to pass

specs/012-filters-tasks/tasks.md

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+# Tasks
+
+## Phase 1: Core Implementation
+- [ ] Task 1.1: Rewrite filters-1 (Blur) task and validations [P]
+- [ ] Task 1.2: Rewrite filters-2 (Grayscale) task and validations [P]
+- [ ] Task 1.3: Rewrite filters-3 (Brightness) task and validations [P]
+- [ ] Task 1.4: Rewrite filters-4 (Drop Shadow) task and validations [P]
+
+## Phase 2: Validation
+- [ ] Task 2.1: Validate JSON against schema
+- [ ] Task 2.2: Run existing test suite
+- [ ] Task 2.3: Format lesson file with Prettier