[pazz]

Shortens urwidtrees/decoration.py without changing behaviour or rendering; found by an audit for over-engineering.

• CollapseIconMixin._construct_collapse_icon builds the left frame, icon and right frame in one loop instead of three copied blocks.
• ArrowTree.decorate returns early for None, drops a second self._indent > 0 check inside a branch that already made it, and drops dead assignments and an always-true None check.
• ArrowTree._construct_connector picks the character first and drops its dead initialisations.
• CollapsibleIndentedTree.decorate and CollapseIconMixin.__init__ lose leftover TODOs, a dead assignment and a stray tuple (cols.append(...),).

Rendering every position of a set of trees through every decorator with indents 0 to 8, all arrow and icon options, collapse states and NestedTree gives byte-identical output on main and this branch (about 88,700 records), under urwid 3.0.4 and 2.1.2, including the cases that raise NoSpaceError.

Review findings and resolution

review-correctness

• A third-party subclass overriding the private _construct_first_indent to return None would now get a TypeError: left; the method never returns None and nothing overrides it.
• Checked without findings: the rendering comparison above; callers of the changed methods; timing on a 1200-level chain and 10000 children.

review-design

• CollapsibleIndentedTree.decorate could return its Columns directly, and _construct_connector had dead initialisations: both done.
• CollapseIconMixin.__init__ is left without a docstring: left; the placeholder said nothing.

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