feat(scheduler-core): implement REPL breakpoints and state inspection (task 12.2)

Adds the interactive simulation REPL's breakpoint and state-inspection
commands (Req 5 AC 22): `break <event_type> [key=value ...]` / `info
break` / `delete <id>|all` on event and decision types, and `info
session/job/queue/worker/resource/summary`.

repl.c (370 lines after task 12.1) couldn't hold this task's full
surface under the project's 800-line cap, so it's split three ways
(matching the snapshot.c/snapshot_wire.c/snapshot_load.c precedent):
repl.c (execution control + dispatch), repl_break.c (matching/CRUD +
the three new driver-facing hooks), repl_info.c (info dumps), sharing
state via repl_internal.h. sim_loop.c gained 3 new bare hook calls
(repl.h inline wrappers, same pattern as task 12.1's two) at the
points design.md's pseudocode requires -- per decoded event before it
joins the batch, per session boundary, and per drained decision --
landing sim_loop.c at exactly 800/800 lines.

Two real bugs found and fixed during development (bug-1506, bug-1507):
an uninitialized xstr_table left breakpoint filter fields silently
NULL instead of failing loud, and repl_breakpoint_free() called a bare
free() on an RTTI-refcounted makeString() string, corrupting the heap.

Review found one gap: `info job` printed only a resreq presence flag
instead of the actual resreq text, when format_resreq() already
existed in this repo for exactly this purpose. Fixed to match.

Scheduler suite: 35/35 clean (was 34/34). RED-phase evidence (2 real
bugs plus 2 synthetic probes, all reverted with confirmed zero
residue) recorded in tasks.md.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JPPXeKSUXUqcqvzNXY1rzJ

src/scheduler/testsuite/test_repl_execution_control.c

@@ -94,6 +94,8 @@
 #include "../src/recording.c"
 #include "../src/recording_session.c"
 #include "../src/repl.c"
+#include "../src/repl_break.c"
+#include "../src/repl_info.c"
 #include "../src/sim.c"
 #include "../src/sim_loop.c"
 #include "../src/sim_record.c"