feat(scheduler-sim-live-allocation): wire simulation mode onto shared picker/allocator (task 4.1)

Replaces sim_picker_thread_fn() (the always-PEND placeholder) with the
real sched_job_picker()/sched_allocator() threads (task 3.1), spawned
against &(sim->core) in sched_sim_driver_run(). Simulation mode now
genuinely uses the jbuf capacity-1 rendezvous for the first time
(confirmed still exactly one producer/one consumer). Adds
sched_election.c to sched_sim_isolation_lib.

Fixes bug-1829 (blocking, only reachable once sim_allocator() actually
called sched_make_allocation() for the first time): core->seqjob_
allocator/parjob_allocator were never bootstrapped for simulation mode
at all. Fixed via new sim_alloc.c (sim_bootstrap_seqjob_allocator()/
sim_bootstrap_parjob_allocator()), mirroring the sim_picker.c/
sim_limit.c precedent.

That fix's own workaround -- a throwaway xce_scheduler_t wrapper
satisfying seqjob/parjob's init_fn -- has a documented, narrow side
effect: prepare_allocation_hook fan-out during a live seqjob/parjob
dispatch attempt reaches the wrapper's own separate plugin registry,
not sim->core.plugins, so a plugin registered only against the real
sim core (the limit plugin) isn't reached for host-scoped matching
during a live dispatch yet. Documented in design.md's new "Known Seam
Gap" section; task 4.3 added to tasks.md to close it before task 5.2's
acceptance test can pass for the host-scoped case.

TDD: new end-to-end test drives a real .replay with an empty decisions
array (ruling out reconciliation) through the real thread pair,
proving a genuine DISPATCH from live resource availability. 25
pre-existing white-box sim/repl test files given link-satisfying
stubs reproducing the OLD always-PEND contract unchanged -- their own
assertions are untouched (task 5.3's job to reconcile deeper).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RLSNJhNoULvVcUhXEFafQC

src/scheduler/meson.build

@@ -19,6 +19,7 @@ scheduler_srcs = [
   'src/sim_loop.c',
   'src/sim_picker.c',
   'src/sim_limit.c',
+  'src/sim_alloc.c',
   'src/sim_verify.c',
   'src/sim_record.c',
   'src/repl.c',
@@ -102,8 +103,8 @@ sched_core_isolation_lib = static_library(
 # the simulation driver's own files, consumed by
 # testsuite/test_sim_isolation.c to prove at build time that
 # sim.c/sim_loop.c/sim_record.c/repl.c/repl_fmt.c/repl_break.c/repl_info.c/
-# repl_params.c/sim_picker.c/sim_limit.c reference zero controller-facing
-# symbols (client/netio/xceapi/delay/idgen). All files are compiled
+# repl_params.c/sim_picker.c/sim_limit.c/sched_election.c reference zero
+# controller-facing symbols (client/netio/xceapi/delay/idgen). All files are compiled
 # together into ONE archive -- task 11.2 added sim_loop.c as a sibling
 # file to task 11.1's sim.c, task 11.5 added sim_record.c as a third, task
 # 12.1 added repl.c as a fourth, task 12.2 added repl_break.c/repl_info.c
@@ -126,13 +127,43 @@ sched_core_isolation_lib = static_library(
 # core_clock.c) never-mechanically-covered gap for the sim driver, which is
 # exactly the omission a prior round of this same task left in place by
 # adding sim_limit.c to scheduler_srcs above without also adding it here.
+# scheduler-sim-live-allocation spec's task 4.1 adds sched_election.c as an
+# eleventh: sim_loop.c's sched_sim_driver_run() now calls sched_job_picker()/
+# sched_allocator() (sched_election.c) directly, no longer the file's own,
+# now-removed sim_picker_thread_fn() -- the same "cover every file the
+# driver's own compiled object actually calls" rationale sim_picker.c/
+# sim_limit.c's own additions above already establish. Task 3.1 (which
+# relocated sched_job_picker()/sched_allocator() out of scheduler.c into
+# this new file) deliberately deferred this addition to task 4.1, since
+# sim_loop.c did not yet call either function until this task wired the
+# real spawn in.
 # Same "compiling to an object is enough, no real linking needed" rationale
-# as sched_core_isolation_lib above.
+# as sched_core_isolation_lib above -- sched_election.c's own undefined
+# references (sched_make_allocation()/sched_commit_decision(), scheduler.c)
+# are themselves already core-safe (verified by task 3.1's own fixture) and
+# remain undefined in this archive exactly like every other cross-file call
+# already does; nm(1)'s FORBIDDEN_SYMBOLS check (test_sim_isolation.c) only
+# flags controller-facing names, none of which sched_election.c references.
+# Task 4.1 also adds sim_alloc.c as a twelfth (bug-1829 fix): sim_loop.c now
+# also calls sim_bootstrap_seqjob_allocator()/sim_bootstrap_parjob_
+# allocator() (sim_alloc.c), the same "cover every file the driver's own
+# compiled object actually calls" rationale as sched_election.c immediately
+# above. sim_alloc.c #includes scheduler.h (for the throwaway xce_scheduler_t
+# wrapper its own file header comment explains) -- safe here for the exact
+# same reason sched_election.c's own scheduler.h include is safe: this file
+# is not part of test_sim_isolation.c's own enumerated text-scan list (that
+# list only ever covered sim.h/sim.c/sim_loop.c/sim_picker.c/sim_record.c/
+# repl.c/repl.h/repl_break.c/repl_info.c/repl_internal.h/repl_params.c, never
+# extended to sim_limit.c or sched_election.c either), and its own compiled
+# object references zero controller-facing symbols (register_seqjob_
+# allocator()/register_parjob_allocator(), plugins/seqjob_allocator.c and
+# plugins/parjob_allocator.c, touch only core-scoped resource/worker state).
 sched_sim_isolation_lib = static_library(
     'sched_sim_isolation',
     ['src/sim.c', 'src/sim_loop.c', 'src/sim_picker.c', 'src/sim_limit.c',
-     'src/sim_record.c', 'src/repl.c', 'src/repl_fmt.c', 'src/repl_break.c',
-     'src/repl_info.c', 'src/repl_params.c', 'src/repl_rollup.c'],
+     'src/sim_alloc.c', 'src/sim_record.c', 'src/repl.c', 'src/repl_fmt.c',
+     'src/repl_break.c', 'src/repl_info.c', 'src/repl_params.c',
+     'src/repl_rollup.c', 'src/sched_election.c'],
     include_directories: incdir,
     dependencies: scheduler_deps,
     install: false)