feat(ui): custom modifier editor in-modal docs, recipes, and attr combobox

Surfaces the contents of docs/user/custom-modifiers.md directly inside
the Custom Modifier Editor so authors can compose descriptors without
cross-referencing the guide:

- Per-primitive docs panel in the Parameter Inspector with a longer
  behaviour explanation + one or more worked examples (collapsible).
- Palette hover tooltips now show the full long description plus the
  first example's headline.
- New 'Templates' header button opens a picker with 5 built-in recipes
  (Boosted Pawn, 3-Charge Shield, Aura King, Vampire, Low-HP Fortress).
- AttrCombobox replaces plain text inputs for attr / targetAttr fields.
  Grouped, free-form autocomplete over 17 curated suggestions with a
  'user-defined' badge for out-of-catalog typed names so ShieldCharges-
  style recipes still work.

Primitives gain optional longDescription + examples fields on their
EffectPrimitive descriptor; 15 registrations annotated. Recipe
descriptors pass the existing validator, and new unit tests enforce
doc coverage going forward.

docs/user/custom-modifiers.md

@@ -17,14 +17,47 @@ modifier profile can reference, exactly the same way it references a built-in.
 2. In the editor's header, click **+ Custom Modifier**. The Custom Modifier
    editor opens as a nested modal.
 3. The Custom Modifier editor is a 3-column workspace:
-   - **Left**: primitive palette, grouped by category.
+   - **Left**: primitive palette, grouped by category. Hover any entry for a
+     full tooltip with the primitive's long description and a worked example.
    - **Center**: the descriptor's primitive tree (the composition you're
      building).
-   - **Right**: parameter inspector for the selected primitive.
+   - **Right**: parameter inspector for the selected primitive. The top of the
+     inspector shows an in-editor docs panel — a longer behaviour explanation
+     plus one or more concrete example configurations you can copy. Click
+     **Hide docs & examples** to collapse it when you want only the form.
 
 Each descriptor needs a **name** (1-40 chars) and an optional **description**
-(0-200 chars). The header also exposes **Save**, **Load from library**, and
-live validation status.
+(0-200 chars). The header exposes **Templates**, **Load**, **Save**, and live
+validation status.
+
+### Templates — starter recipes
+
+The **Templates** button opens a picker with pre-composed recipes drawn from
+the examples below (Boosted Pawn, 3-Charge Shield, Aura King, Vampire,
+Low-HP Fortress). Picking a template replaces the current draft with a fresh
+copy — the id is regenerated so you can save the loaded template as your own
+library entry without collisions.
+
+### Attribute-name autocomplete
+
+Primitives that target an attribute (`seed-attribute`, `add-to-attribute`,
+`multiply-attribute`, `absorb-damage-with-attribute`, `add-aura`) render
+their `attr` / `targetAttr` field as a **combobox** with grouped
+suggestions:
+
+- **Core numeric attributes** — Hp, HpBonus, RangeBonus, DamageResistance,
+  ReflectDamagePercent, AbsorbDamageRate, HalfmoveClock, FullmoveNumber.
+  Safe targets for add/multiply/aura/absorb primitives.
+- **Core non-numeric attributes** — CaptureFlags, DirectionAdditions,
+  PromotionOverride, BlockedMoveTypes, AbsorbDamageAttr, HasMoved. Seed-only
+  for most; avoid add/multiply.
+- **User-defined examples** — ShieldCharges, ArmorPlates, BloodStacks,
+  ManaPool. Illustrative names matching the recipes; invent your own.
+
+The combobox is **free-form** — type any name and hit Enter to accept it,
+even if it isn't in the list. Typed values not in the catalog get a small
+`user-defined` badge so you know you're outside the schema. Numeric-context
+primitives (add, multiply, aura, absorb) rank numeric suggestions first.
 
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