[flyingfoxyy]

Summary

fabsorb removed a multi-fanout LUT whenever every fanout still fit in K inputs, implicitly assuming that removing one LUT always saves one LUT. When a LUT library is installed, LUT area depends on its input count, so that assumption can increase area.

This PR renames the command to lutabsorb and makes it library-aware:

• Effective K is capped by the library's LutMax. The default is min(6, LutMax); an explicit -K above LutMax is truncated with a warning.
• A candidate is absorbed only when area(u) + sum(area(v_old)) - sum(area(v_new)) > 0, using pLutAreas[fanin_count] from the installed library. The total area gain is reported.
• Candidates involving nodes with more fanins than LutMax are skipped, since the library cannot price them.

The rename covers the command, the Abc_NtkLutAbsorb API, the source file, and the build lists. With the default 4-input library (unit areas) the gain equals the number of removed LUTs, so existing behavior is preserved.

Tests

• make -j$(nproc) succeeds.
• Integration cases cover K truncation (default and 6-input libraries), negative/positive area gain, and default K = min(6, LutMax).
• r i10.aig; if -K 4; lutabsorb; cec and read_lut (6-input area lib); r i10.aig; if; lutabsorb; cec both remain equivalent.
• The CI smoke command and test/mf_maprefs_overflow.sh pass.