feat(types): tagified content as immutable sibling classes (#116)

CHANGELOG.md

@@ -9,39 +9,21 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Breaking changes
 
-* `Tagifiable.tagify()` now returns `Tagified`, a tighter type that
-  excludes the un-resolved `Tagifiable` arm of `TagNode`. Custom
-  `.tagify()` implementations annotated with bare `TagList` or `Tag`
-  return types will fail static type checking; update them to
-  `-> Tagified` (or omit the return annotation). Runtime behavior of
-  correct `.tagify()` implementations is unchanged. (#105)
+* `Tagifiable.tagify()`'s return annotation is now `Tagified`, a new type alias for the union of fully-tagified shapes (`TagifiedNode | float | None | Sequence[Tagified]`, mirroring `TagChild`). Custom `.tagify()` implementations annotated with bare `TagList` / `Tag` return types should switch to `-> Tagified`, or drop the annotation. Runtime behavior of correct implementations is unchanged. (#105, #116)
 
-* `Tag.tagify()` no longer preserves the caller's `Tag` subclass in
-  its return type. Code relying on the previous subclass-preserving
-  signature should `cast` the result. (#105)
+* The result of `.tagify()` is now **immutable**. Calling `.append`, `.extend`, `.insert`, `.add_class`, `__setitem__`, or the context-manager `with` form on a tagified value raises `AttributeError` and is a static type error. Mutate on the buildable `Tag` / `TagList` side, then call `.tagify()` once to produce the render-ready result. (#116)
 
-### New features
-
-* `Tag` and `TagList` are now generic in their child type, defaulting
-  to `TagNode`. Bare `Tag` / `TagList` retain today's meaning. Mutation
-  methods (`append` / `extend` / `insert`) still accept `Tagifiable` at
-  static-type-check time even on tagified containers — the invariant
-  is enforced at runtime instead (`TagList.tagify()` raises `TypeError`
-  and `get_html_string` raises `RuntimeError` for an un-tagified
-  subtree). See `tests/test_types.py` for the rationale. (#105)
+* `TagList.tagify()` now raises `TypeError` at the boundary when a child's `.tagify()` returns un-tagified content (e.g. a bare `TagList` containing a still-`Tagifiable` object). The error names the offending class and slot index so buggy `.tagify()` implementations surface at the source. The render-time `RuntimeError` for the same family of violations has been clarified. (#7, #105, #112, #116)
 
-* Added the public type alias `Tagified` — the union of all
-  fully-tagified shapes — for use as the return annotation of
-  `Tagifiable.tagify()` implementations. (#105)
+### New features
 
-### Bug fixes
+* Exported the new tagified sibling classes `TagifiedTag` and `TagifiedTagList`. Use them in narrow annotations (`def f(t: TagifiedTag): ...`) and `isinstance` checks on `.tagify()` output. (#116)
 
-* `TagList.tagify()` now raises `TypeError` at the boundary when a child's `.tagify()` returns a `TagList` containing an un-tagified `Tagifiable` object. The error names the offending class and slot index so buggy `.tagify()` implementations surface at the source rather than later at render time. The render-time `RuntimeError` raised by `get_html_string()` for an un-tagified child has also been clarified to include the offending class name and a hint that the tree was likely mutated after `.tagify()` was called. (#7, #105, #112)
+* Added `is_tagified(x)` for runtime distinguishability between buildable `Tag` / `TagList` and their tagified counterparts. Returns a `TypeIs[...]` so pyright narrows at call sites. (#116)
 
 ### Dependencies
 
-* Bumped `typing_extensions` floor to `>=4.12.0`, required for
-  PEP 696 `TypeVar(default=...)` support on Python 3.13+.
+* Bumped `typing-extensions` floor to `>=4.12.0`.
 
 ### Other changes