Restructure documentation TOC and fix constraint dimension functions

- Flatten manual-model.md and manual-solution.md TOC: promote component sections
  from ### to ## level for better sidebar navigation
- Replace static Content lists with Documenter @contents blocks (Depth = 2)
- Redistribute Model predicates across logical sections:
  - has_variable/is_variable/is_nonvariable → Variable section
  - has_control/is_control_free → Control section
  - has_abstract_definition/is_abstractly_defined → Problem definition
  - is_nonautonomous → Time dependence
- Remove standalone Model predicates section
- Fix constraint dimension functions:
  - Restore dim_state_constraints_box, dim_control_constraints_box,
    dim_variable_constraints_box for Model (constraint counts)
  - Keep dim_dual_*_constraints_box for Solution (dual dimensions)
- Update imports, tests, and API documentation to include both families
- Remove Draft = false meta blocks from markdown files (use make.jl draft mode)
- Enable
- Flatten manual-model.md and manual-solution.md TOC: promo

Author: ocots

docs/make.jl

@@ -153,7 +153,7 @@ cp(
 Draft = false
 ```
 =#
-draft = true  # Draft mode: if true, @example blocks in markdown are not executed
+draft = false  # Draft mode: if true, @example blocks in markdown are not executed
 
 # ═══════════════════════════════════════════════════════════════════════════════
 # Load extensions

docs/src/api/public.md

@@ -58,10 +58,13 @@ definition
 expression
 describe
 dim_boundary_constraints_nl
+dim_control_constraints_box
 dim_dual_control_constraints_box
 dim_dual_state_constraints_box
 dim_dual_variable_constraints_box
 dim_path_constraints_nl
+dim_state_constraints_box
+dim_variable_constraints_box
 dimension
 discretize
 dual