fix(exec): release the input table of window, sort and limit queries

[ser-vasilich]

Bug

A windowed, sorted or limited query leaks its input table once per call.

Every node the executor evaluates returns an owned reference; the constant table node a query is rooted on is no exception, it retains its literal (OP_CONST, src/ops/exec.c). The OP_WINDOW, OP_SORT and both OP_HEAD branches released their input only when it differed from the graph's table, taking an equal pointer for a borrowed reference. A query's root is a constant node over that very table, so the reference was never released.

While the input is a global the leak is one reference on an object that stays alive anyway, so nothing grows. When the input is built for the call — (select {from: (concat a b) asc: k}), a window over a projection, a limited select over a filtered table — the whole input table stays allocated after every call. A service that windowed a freshly concatenated buffer on a timer grew by one buffer per pass with every global flat (#602).

Fix

The four cases release their input on every path, as the join and the plain head/tail cases already did; the reduction case, which carried the same guard without a reachable shape, is aligned with them. No result changes; a shared input keeps its lifetime.

Tests

• test/rfl/mem/query_input_release.rfl: window, sorted and limited selects over a table built per call, with the two-window bytes-allocated method of the other memory probes, plus a shared input reused across fifty calls. Every probe fails on the unfixed executor.
• test/test_lang.c lang/select/releases_input_table: twenty calls of each shape over one table; its refcount must be exactly what it was before. Fails on the unfixed executor at the first window shape.

Fixes #602.