Standardize private/public method naming conventions

[ocots]

Overview

This PR standardizes the naming conventions for private and public methods across CTBase.jl, following the newly documented conventions in dev/philosophy/modules.md.

Changes

Documentation Updates

1. dev/philosophy/modules.md — Added explicit naming conventions:

   • symbol — public: exported via export; part of the documented API
   • _symbol — private helper: unexported; internal implementation detail
   • __symbol — default value: unexported; provides a replaceable semantic default

2. dev/planning.md — Improved checkpoint templates:

   • MCP get_test_command preferred for running tests
   • Fallback commands provided for when MCP is unavailable
   • Clear distinction between phase-specific and full-suite checkpoints

Code Refactoring

3. src/Descriptions/ — Renamed private helper functions:

   • compute_similarity → _compute_similarity
   • find_similar_descriptions → _find_similar_descriptions
   • format_description_candidates → _format_description_candidates

4. src/Exceptions/display.jl — Renamed private helper functions:

   • extract_user_frames → _extract_user_frames
   • format_user_friendly_error → _format_user_friendly_error
   • ansi_color → _ansi_color
   • ansi_reset → _ansi_reset
   • print_ansi_styled → _print_ansi_styled

5. src/Extensions/Extensions.jl — Confirmed __display as a default value (double underscore convention)

Test Updates

6. test/suite/descriptions/test_similarity.jl — Updated all calls to renamed functions

7. test/suite/exceptions/test_display.jl — Updated calls to renamed functions

8. test/suite/extensions/test_extensions_enriched.jl — Fixed extension stub testing:

   • Added fake types (FakeDocumenterReferenceTag, FakeCoveragePostprocessingTag, FakeTestRunnerTag)
   • Follows testing-creation.md §6 to prevent flaky tests when extensions are loaded elsewhere
   • Removed conditional UndefVarError checks in favor of deterministic fake types

Rationale

The naming convention clarification makes the intent of each symbol explicit:

• Public symbols are exported and documented
• Private helpers (_prefix) are internal implementation details
• Default values (__prefix) are semantic defaults that can be overridden by extensions or subtypes

This aligns with the broader effort (PR #438) to improve code organization and documentation across the control-toolbox ecosystem.

Testing

All affected test suites pass:

• test/suite/descriptions/test_similarity.jl
• test/suite/exceptions/test_display.jl
• test/suite/extensions/test_extensions_enriched.jl

[ocots]

Summary of Changes

This PR addresses the "Private/public method naming and distribution" item from PR #438's planned features.

What was done

1. Documented naming conventions in dev/philosophy/modules.md:

   • symbol (no prefix) → public, exported, part of documented API
   • _symbol (single underscore) → private helper, internal implementation detail
   • __symbol (double underscore) → default value, replaceable semantic default

2. Renamed private helper functions to follow the _prefix convention:

   • In Descriptions: compute_similarity, find_similar_descriptions, format_description_candidates
   • In Exceptions: extract_user_frames, format_user_friendly_error, ansi_color, ansi_reset, print_ansi_styled

3. Improved planning documentation with better checkpoint templates (MCP-first approach)

4. Fixed extension stub testing to use fake types per testing-creation.md §6, preventing flaky tests when extensions are loaded elsewhere in the test suite

Impact

• No API changes (only private helpers renamed)
• All tests updated and passing
• Clearer intent for symbol visibility across the codebase
• Aligns with the broader refactoring effort in PR Infrastructure improvements: DeepWiki, Traits, and documentation enhancements #438