feat(executor): implement ILIKE [CLAUDE]

[jbylund]

The gap

ILIKE is absent from the executor's ENV entirely, so both it and NOT ILIKE raise rather than answering:

>>> execute("SELECT s FROM t WHERE s ILIKE 'bump%'", tables=t).rows
ExecuteError: Step 'Join: t (...)' failed: name 'ILIKE' is not defined

This is the loose end from #8139, which taught the generator to honor negate on both Like and ILike — so the flag now reaches an ILIKE the ENV cannot resolve.

The change

ILIKE is LIKE with re.IGNORECASE, through one shared helper so the two cannot drift. The escaping and anchoring from 44b73a0 is exactly what ILIKE needs, and that expression moves into the helper unchanged.

ILIKE 'bump%'          -> ['Bump Version']
ILIKE '%version'       -> ['Bump Version', 'B.mp Version']
NOT ILIKE 'bump%'      -> the rest
ILIKE 'b.mp version'   -> ['B.mp Version']                    -- '.' is literal
ILIKE 'b_mp version'   -> ['Bump Version', 'B.mp Version']    -- '_' is the wildcard

Tests

Each pattern is run in both cases and expected to give the same rows, which is the property that actually distinguishes ILIKE from LIKE. Hand-cased patterns assert it only incidentally: they would still pass with IGNORECASE dropped, for whichever spelling happened to match. Verified by removing re.IGNORECASE — the test fails immediately.

The table carries "B.mp Version" alongside "Bump Version" so the . rows discriminate a literal dot from the _ wildcard, rather than only asserting a non-match.

Full suite: 1317 tests, OK.