ifcmcp: source tool descriptions from ifcquery/ifcedit instead of duplicating them

Alternative to #8955, for #8951 (23 of 25 ifcmcp tools reach MCP clients
with an empty description because FastMCP reads each wrapper's own
__doc__, and the server.py wrappers had none).

#8955 fixes this by hand-writing a new docstring directly onto each
server.py wrapper. Most of those wrappers are thin passthroughs to
IfcSession methods in core.py, which already had short docstrings, which
themselves mostly delegate to already-documented ifcquery/ifcedit
functions -- so that fix tripled up content across three layers that can
drift out of sync.

This instead enriches the true source (the ifcquery/ifcedit library
functions, useful independently of MCP) and has core.py's IfcSession
methods copy __doc__ from their delegate via a small _use_doc()
decorator, and server.py's tool registration pull description= from the
matching IfcSession method. Methods that aren't pure passthroughs
(session lifecycle, generic API/shape dispatch) keep their own
hand-written docs. Keeps #8955's regression test.

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