Two correctness fixes found during final Phase 6 code review:
F1 (CRITICAL): GC permanently disabled — staging_merge_complete bootstrapping deadlock.
sched_begin_session reset staging_merge_complete to 0 but never set it back to 1,
so sched_end_session's guard (!staging_merge_complete) always fired, preventing GC
from ever running. select-node memory leaked indefinitely across scheduling sessions.
Fix: set staging_merge_complete=1 at the end of sched_begin_session after all
staging work (sched_account_jobs etc.) completes.
F2 (HIGH): recompact_node_ids() omitted from GC protocol in sched_end_session.
The protocol in resreq.h requires gc_sweep → recompact_node_ids. Without
recompaction, sel_node_next_id grows monotonically across sessions and
select_eval_ctx_t arrays (sized by max node_id) grow without bound.
Fix: call recompact_node_ids() after gc_sweep_select_nodes.
Also adds test_staging_merge_complete_gc_guard to document the bootstrap
invariant: sched_begin_session must leave staging_merge_complete=1 so the
GC guard in sched_end_session does not fire.
Replace the always-return-1 stub with a real implementation that:
- Returns 1 immediately when s == NULL or s->root == NULL (no constraint)
- Builds a host_eval_ctx_t from w->resvals and calls eval_select_simple
- Uses a zero-resource stack context when resvals.caps == 0 so constant
sub-expressions (SEL_TRUE, SEL_FALSE, SEL_ANY) still evaluate correctly
- On OOM (build_host_eval_ctx returns NULL), conservatively passes the host
- Maps eval_select_simple result: >0 → 1 (match), <=0 → 0 (no-match)
Add #define UNIT_TEST 1 to test.c, remove redundant #ifdef guard, and
add three new TDD tests covering NULL select, SEL_TRUE, and SEL_FALSE.
All 6 tests pass.
