docs: add impl-level filter categories to API and Plausible docs

- Add 5 impl-level URL params: dep, tech, pat, prep, style
- Update category values reference with spec/impl distinction
- Add filter_* properties for og:image tracking
- Update API response example with impl-level counts

Author: MarkusNeusinger

docs/reference/api.md

@@ -160,13 +160,22 @@ The pyplots API is a **FastAPI-based REST API** serving plot data to the fronten
 **Purpose**: Filter plots with faceted counts for all filter categories
 
 **Query Parameters** (combinable):
+
+*Spec-level filters (WHAT is visualized):*
 - `lib` - Library filter (matplotlib, seaborn, etc.)
 - `spec` - Spec ID filter
 - `plot` - Plot type tag filter
 - `data` - Data type tag filter
 - `dom` - Domain tag filter
 - `feat` - Features tag filter
 
+*Impl-level filters (HOW it is implemented):*
+- `dep` - Dependencies filter (scipy, sklearn, etc.)
+- `tech` - Techniques filter (twin-axes, annotations, etc.)
+- `pat` - Patterns filter (data-generation, groupby-aggregation, etc.)
+- `prep` - Dataprep filter (kde, binning, regression, etc.)
+- `style` - Styling filter (minimal-chrome, alpha-blending, etc.)
+
 **Filter Logic**:
 - Comma-separated values: OR (`lib=matplotlib,seaborn`)
 - Multiple params same name: AND (`lib=matplotlib&lib=seaborn`)
@@ -192,7 +201,12 @@ The pyplots API is a **FastAPI-based REST API** serving plot data to the fronten
     "plot": {"scatter": 10},
     "data": {"numeric": 15},
     "dom": {"statistics": 8},
-    "feat": {"basic": 12}
+    "feat": {"basic": 12},
+    "dep": {"scipy": 3},
+    "tech": {"annotations": 5},
+    "pat": {"data-generation": 8},
+    "prep": {"kde": 2},
+    "style": {"alpha-blending": 4}
   },
   "globalCounts": {...},
   "orCounts": [...]

docs/reference/plausible.md

@@ -23,7 +23,7 @@ Filters create dynamic URLs with the following format:
 https://pyplots.ai/{category}/{value}/{category}/{value}/...
 ```
 
-**Ordered categories**: `lib`, `spec`, `plot`, `data`, `dom`, `feat`
+**Ordered categories**: `lib`, `spec`, `plot`, `data`, `dom`, `feat`, `dep`, `tech`, `pat`, `prep`, `style`
 
 **Examples**:
 - `/?lib=matplotlib` → `https://pyplots.ai/lib/matplotlib`
@@ -213,17 +213,23 @@ To see event properties in Plausible dashboard, you **MUST** register them as cu
 | `method` | Action method (card, image, tab, click, space, doubletap) | `copy_code`, `random` |
 | `page` | Page context (home, catalog, spec_overview, spec_detail) | `copy_code`, `download_image`, `og_image_view` |
 | `platform` | Bot/platform name (twitter, whatsapp, teams, etc.) | `og_image_view` |
-| `category` | Filter category (lib, plot, dom, feat, data, spec) | `search`, `random`, `filter_remove` |
+| `category` | Filter category (lib, spec, plot, data, dom, feat, dep, tech, pat, prep, style) | `search`, `random`, `filter_remove` |
 | `value` | Filter value | `random`, `filter_remove` |
 | `query` | Search query text | `search`, `search_no_results` |
 | `destination` | External link target (linkedin, github, stats) | `external_link` |
 | `tab` | Tab name (code, specification, implementation, quality) | `tab_click` |
 | `size` | Grid size (normal, compact) | `toggle_grid_size` |
 | `filter_lib` | Library filter value (for og:image) | `og_image_view` |
-| `filter_dom` | Domain filter value (for og:image) | `og_image_view` |
+| `filter_spec` | Specification filter value (for og:image) | `og_image_view` |
 | `filter_plot` | Plot type filter value (for og:image) | `og_image_view` |
-| `filter_feat` | Features filter value (for og:image) | `og_image_view` |
 | `filter_data` | Data type filter value (for og:image) | `og_image_view` |
+| `filter_dom` | Domain filter value (for og:image) | `og_image_view` |
+| `filter_feat` | Features filter value (for og:image) | `og_image_view` |
+| `filter_dep` | Dependencies filter value (for og:image) | `og_image_view` |
+| `filter_tech` | Techniques filter value (for og:image) | `og_image_view` |
+| `filter_pat` | Patterns filter value (for og:image) | `og_image_view` |
+| `filter_prep` | Dataprep filter value (for og:image) | `og_image_view` |
+| `filter_style` | Styling filter value (for og:image) | `og_image_view` |
 
 ### Goals Configuration
 
@@ -378,12 +384,20 @@ unknown
 
 ### `category` Values
 ```
+# Spec-level (WHAT is visualized)
 lib   # library filter
+spec  # specification filter
 plot  # plot_type filter
+data  # data_type filter
 dom   # domain filter
 feat  # features filter
-data  # data_type filter
-spec  # specification filter
+
+# Impl-level (HOW it is implemented)
+dep   # dependencies filter
+tech  # techniques filter
+pat   # patterns filter
+prep  # dataprep filter
+style # styling filter
 ```
 
 ### `tab` Values