Add sinh, cosh, tanh pushdown support

[sfc-gh-amzheng]

Closes #45

Problem

sinh, cosh, and tanh are not in the shippable built-in functions list, so queries using them cannot be pushed down to DuckDB. Their inverses (asinh, acosh, atanh) were already shippable.

Solution

Add sinh, cosh, and tanh to ShippableBuiltinProcs in shippable_builtin_functions.c, matching the pattern already used for the inverse functions.

-- Pushed down to DuckDB instead of executed in PostgreSQL
SELECT sinh(x), cosh(x), tanh(x) FROM my_iceberg_table;

Test plan

• New pytest suite test_mathematical_functions_pushdown.py covers all three functions with pushdown verification

[sfc-gh-okalaci]

conditional approval: good to go once the test suggestions below are applied. i checked sinh/cosh/tanh against postgres across a wide range (denormals, overflow, ±inf, nan) and they match bit-for-bit, so no wrapper is needed here, that part is correct.

two non-blocking notes:

• the commit message says it also fixes pre-commit stage names (pre-commit -> commit), but that's not in this diff, and our .pre-commit-config.yaml already uses stages: [pre-commit] (the newer name). looks copied from somewhere else, can we drop that line from the message?
• looks like #118 does the same three functions. this one follows the review there (no wrappers, just the shippable list), so it looks like the better version. we should close #118 to avoid confusion.

if you hit any issues applying these, let me know.

[sfc-gh-okalaci]

can we add a few normal values here too? like 0.01, 0.5, 1.25, 2.5, some negatives, and -0.0. right now it's only 0/±1 which is a bit thin.

would be nice to also cover inf/-inf/nan, those are the interesting ones for these funcs. note though they won't work with this assert: assert_query_results_on_tables does abs(a-b) <= tol, and inf-inf/nan-nan is nan, so it fails even when both sides match. for those we'd need an exact compare, or assert_table_contents_match (uses EXCEPT ALL, where pg treats inf = inf and nan = nan).

[sfc-gh-okalaci]

small: update this line too once the values change, it says only 0, -1, 1, NULL.