xce_alloc_plan_iter_t.init takes xce_sched_core_t* instead of
xce_scheduler_t*; both built-in generators, both allocators' call sites
and the contract-test stub follow. The parjob purity test now shows an
identical plan sequence for a NULL and a poisoned core.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Defines xce_alloc_plan_t (partition of a job's task count into
per-host slot buckets), xce_alloc_plan_iter_t, and xce_host_iter_t
(init/next/fini vtables, stack-allocate-then-init-in-place convention
matching sched_ctx_init) as reusable abstractions any allocator can
adopt. Proven usable by a trivial no-op reference implementation and
a fresh-per-bucket host_iter composition test, no allocator wired in
yet.
Task 1.1 (scheduler-allocation spec). Requirements 2.1, 3.1.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XYdtrEWWZfKRRGED7raEYg
