Migrate `mingling_core::pathf` into `mingling_core::builds::pathf` and
re-export from `mingling::build`.  Update all references from
`mingling::builds` and `mingling::pathf` to `mingling::build`.

Add empty template directories for command, flat, and modularity
layouts under template_0.2. Revise CHECKLIST to include project
description prompt and pre-initialization step, reorder feature
checklist, and fix a trailing whitespace.

Add the `pathf` feature to mingling dependency and invoke
`analyze_and_build_type_mapping` during the build script.

Reorganize internal module visibility from `mod + pub use` to
direct `pub mod`.

Parse fenced code blocks as key-value pairs and checkbox lines as
namespace toggles in a single pass

Extract duplicate `MockCollect` implementations into a reusable
`MockProgramCollect` type. Conditionally require `Serialize` on the
`Groupped` trait when the `general_renderer` feature is enabled.