feat: full schema export — 79 nodes including all zenfilters and codecs

Schema now includes all registered nodes when nodes-all feature is used:
- 38 zenfilters (Exposure, Contrast, Saturation, Clarity, Sharpen,
  Vignette, Grain, Dehaze, ColorGrading, Levels, HslAdjust, etc.)
- 15 codec encode/decode nodes (JPEG, Mozjpeg, PNG, WebP lossy/lossless,
  GIF, AVIF, JXL, TIFF, BMP, HEIC decode, WebP decode, JPEG decode,
  JXL decode)
- 11 geometry nodes (Crop variants, Flip, Rotate, Orient, Region, etc.)
- 6 RIAPI adapter nodes (flip, rotate, autorotate, crop, frame)
- 5 pipeline nodes (CropWhitespace, FillRect, RoundCorners, Composite,
  Overlay, RemoveAlpha)
- 4 layout/resize nodes (Constrain, Resize, OutputLimits)
- 1 quality intent node (format/quality selection)

106 RIAPI querystring keys documented.
Doc generator produces 79 node pages + index + QS reference + formats.

Author: lilith

tools/docgen/sample_schemas/v3_codecs.json

@@ -68,7 +68,7 @@
       "supports_lossless": true
     },
     {
-      "can_decode": false,
+      "can_decode": true,
       "can_encode": false,
       "extension": "avif",
       "extensions": [
@@ -84,7 +84,7 @@
       "supports_lossless": true
     },
     {
-      "can_decode": false,
+      "can_decode": true,
       "can_encode": false,
       "extension": "jxl",
       "extensions": [
@@ -119,8 +119,8 @@
       "supports_lossless": false
     },
     {
-      "can_decode": false,
-      "can_encode": false,
+      "can_decode": true,
+      "can_encode": true,
       "extension": "bmp",
       "extensions": [
         "bmp"
@@ -136,8 +136,8 @@
       "supports_lossless": true
     },
     {
-      "can_decode": false,
-      "can_encode": false,
+      "can_decode": true,
+      "can_encode": true,
       "extension": "tiff",
       "extensions": [
         "tiff",
@@ -153,8 +153,8 @@
       "supports_lossless": true
     },
     {
-      "can_decode": false,
-      "can_encode": false,
+      "can_decode": true,
+      "can_encode": true,
       "extension": "pnm",
       "extensions": [
         "pnm",
@@ -177,8 +177,8 @@
       "supports_lossless": true
     },
     {
-      "can_decode": false,
-      "can_encode": false,
+      "can_decode": true,
+      "can_encode": true,
       "extension": "ff",
       "extensions": [
         "ff"