docs: complete the 5.4.5 changelog entry

The release script dropped every scoped feat:/fix: commit from the
generated entry (fixed in the prior commit); this backfills the mini
client presence feature and both C-client fixes.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uc9V1v7iXruubpoLiSE24M

CHANGELOG.md

@@ -4,8 +4,14 @@ All notable changes to this project are documented here, organized by release.
 
 ## [5.4.5]
 
+### Added
+- `hbc_mini.py` and `hbc_mini.c` (the dependency-free clients) get the same per-protocol connectivity probe as `hbc`: `p4`/`p6` flags on every heartbeat and a `connectivity` metric (presence, own address, gateway, RTT) via `network_monitor`, with gateway lookup on Linux, FreeBSD/NetBSD/DragonFly (both clients) and macOS/Windows (`hbc_mini.py` only)
+- `scripts/c/test_probe.c` and a `make test` target — the C client's first automated test suite
+
 ### Fixed
-- shutdown ordering, silent probe failures, and unused import in the mini clients
+- `hbc_mini.c`: the clean-shutdown heartbeat could be delayed or lost behind an in-flight connectivity probe on SIGTERM; it is now sent before the probe thread is joined
+- `hbc_mini.c`: a connectivity probe that fails to start, or is configured with a non-IP-literal target, now logs a warning instead of failing silently
+- `hbc_mini.py`: removed an unused import
 
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