Unify ANSI display formatting in Core module

[ocots]

Summary

Centralizes all ANSI formatting utilities in Core/display.jl to provide a single source of truth for terminal color support across the package.

Changes

New files

• src/Core/display.jl — ANSI formatting primitives:

  • _apply_ansi(s, code, io::IO) — base function with color detection
  • Semantic wrappers: _dim, _bold, _red, _yellow, _green
  • get_format_codes(io::IO) — semantic palette for structured display
  • Bug fix: supports_color = true → get(io, :color, false) (detection was commented out)

• src/Core/tags.jl — Moved AbstractTag from display.jl (better organization)

• test/suite/core/test_core_display.jl — Comprehensive tests (52 assertions):

  • Tests color detection (with/without color)
  • Tests all ANSI wrappers
  • Tests get_format_codes NamedTuple structure

Modified files

• src/CTBase.jl — Changed load order: Core before Exceptions (was stale comment "must load first")
• src/Core/Core.jl — Added include("display.jl") and include("tags.jl")
• src/Exceptions/Exceptions.jl — Added using ..Core: Core for qualified access
• src/Exceptions/display.jl — Removed local ANSI definitions, now uses qualified calls (Core._dim, Core._bold, etc.)

Philosophy compliance

• No top-level exports — ANSI functions use underscore prefix, not exported
• Qualified imports — Exceptions uses Core._dim instead of using ..Core: _dim
• Single source of truth — All ANSI formatting centralized in Core

Testing

All tests pass (1242/1242), including:

• New test_core_display.jl (52/52)
• Existing test_exception_display.jl (155/155)