Update design doc and spec with trait value table and fixed-size index

Author: sugmanue

designs/compact-binary-model-format.md

@@ -260,6 +260,8 @@ performance), the remaining 30-40% matters.
 ├────────────────────────────────┤
 │ Symbol Table                   │
 ├────────────────────────────────┤
+│ Trait Value Table              │
+├────────────────────────────────┤
 │ Shape Index (optional)         │
 ├────────────────────────────────┤
 │ Metadata Section               │
@@ -360,6 +362,28 @@ Writers SHOULD assign local symbol IDs in descending frequency order (most
 frequently referenced strings get the lowest IDs) to minimize VarUInt
 encoding size.
 
+### Trait Value Table
+
+The trait value table deduplicates trait values that appear multiple times
+across shapes. Each unique trait value is stored once in this table and
+referenced by index from within shape trait encodings.
+
+```
+VarUInt         valueCount
+DynamicValue[]  values (valueCount complete encoded values)
+```
+
+In the shapes section, each trait is encoded as:
+
+```
+SymRef    traitId
+VarUInt   traitValueRef (index into the trait value table)
+```
+
+This replaces inline `DynamicValue` encoding with a compact integer reference.
+Annotation traits (`{}`) that appear thousands of times are stored once and
+referenced by a 1-2 byte VarUInt instead of being encoded inline each time.
+
 ### Shape Index
 
 The shape index maps shape IDs to byte offsets within the shapes section and

docs/source-2.0/spec/smf.rst

@@ -56,6 +56,8 @@ File structure
     ├────────────────────────────────┤
     │ Symbol Table                   │
     ├────────────────────────────────┤
+    │ Trait Value Table              │
+    ├────────────────────────────────┤
     │ Shape Index (optional)         │
     ├────────────────────────────────┤
     │ Metadata Section               │
@@ -138,6 +140,24 @@ Writers SHOULD assign local symbol IDs in descending frequency order to
 minimize VarUInt encoding size.
 
 
+.. _smf-trait-value-table:
+
+-----------------
+Trait value table
+-----------------
+
+Deduplicates trait values that appear multiple times across shapes. Each
+unique value is stored once and referenced by index.
+
+.. code-block:: none
+
+    VarUInt         valueCount
+    DynamicValue[]  values (valueCount encoded values)
+
+In shapes, each trait is encoded as ``SymRef traitId`` + ``VarUInt valueRef``
+(index into this table) instead of an inline ``DynamicValue``.
+
+
 .. _smf-shape-index:
 
 -----------