feat(scheduler-sim-diagnostics): display effective host-scope note (Req 1.6)

repl_info_limit() now prints an explanatory note when a limit is implicitly
host-scoped (is_host_based_limit() > 0 due to a percent-based value on a
non-shared resource) but its own configuration doesn't show an explicit
per-host scope. The real discriminator turned out to be consumers[CONSUMER_
HOST]->per_consumer, not pointer-nullity as design.md's gloss said --
build_consumer() unconditionally allocates a consumer for all four
dimensions, so the struct field is never actually NULL in production. Fixed
using the same field is_host_based_limit() itself already falls back to;
verified via RED-phase reproduction that the literal design.md condition
never fires. design.md corrected to document the real condition.

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

.kiro/specs/scheduler-sim-diagnostics/tasks.md

@@ -23,7 +23,7 @@
   - Observable: a limit configured with an exclusion group ("all except X") shows both the inclusion and the exclusion in its output; `info limit all` against a fixture with multiple configured limits displays every one's setting
   - _Requirements: 1.1, 1.2, 1.5_
 
-- [ ] 2.3 Display effective host-scope for implicitly host-scoped limits
+- [x] 2.3 Display effective host-scope for implicitly host-scoped limits
   - After `fmt_limit()`'s output, call `is_host_based_limit(core->resmgr, limit)`; if it returns `> 0` AND the limit's own per-host consumer is not configured, print an explanatory host-scope note
   - Observable: two REPL fixtures — one percent-based limit on a per-host resource without explicit per-host scoping (note appears), one absolute-value or explicitly-global-scoped limit (note does not appear)
   - _Requirements: 1.6_