Use N-term telescoping for compiled inner joins

[ila]

Summary

• add an exact N-term telescoping strategy for compile-only, simple-projection inner joins over regular tables
• reconstruct each old relation as R_old = R_now - delta_R, reducing an N-way join from 2^N - 1 delta terms to N terms
• retain the existing inclusion-exclusion strategy for native refresh, outer joins, DuckLake, and unsupported leaf shapes
• expose openivm_regular_nterm as a guarded setting and propagate it into compiled refresh planning

For a three-way join, the generated delta is:

delta_R JOIN S_old JOIN T_old
UNION ALL
R_now JOIN delta_S JOIN T_old
UNION ALL
R_now JOIN S_now JOIN delta_T

where each old-state input is reconstructed with signed multiplicities from the current table and its delta. This preserves exact Z-set semantics while avoiding the seven inclusion-exclusion terms otherwise required for three inputs.

Tests

• make test — 55/55 suites, 7,538 assertions
• focused join/compile suites — 475 assertions
• mixed INSERT + UPDATE + DELETE self-join test with EXCEPT ALL bag-equality checks in both directions
• TPC-DI SF1 rewriter benchmark — 45/45 incremental; 44/44 successful refreshes correct; only the pre-existing q40 ICU/collation binder failure
• manual full-pipeline shape benchmark: fact_trade 15.52/16.79s to 10.22/10.33s; fact_holdings 22.45/18.79s to 12.30/15.19s