Update design docs for heartbeat, auto-reconnect, handshake retry, and sim improvements

fips-link-layer.md:
- Rewrite Liveness Detection: explicit Heartbeat (0x51) with 10s interval
  and 30s dead timeout replaces vague gossip-as-heartbeat description
- Add Auto-Reconnect section: MMP dead timeout triggers retry with
  unlimited backoff for auto_reconnect peers
- Add Handshake Message Retry section: link + session layer resend with
  exponential backoff within timeout window
- Add Heartbeat to Link Message Types table
- Update Implementation Status with three new implemented features

fips-configuration.md:
- Add handshake_resend_interval_ms, handshake_resend_backoff,
  handshake_max_resends to rate_limit table
- Add heartbeat_interval_secs, link_dead_timeout_secs to general table
- Add peers[].auto_reconnect to peers table
- Note auto-reconnect bypasses max_retries in retry section
- Update complete reference YAML with all new parameters

fips-wire-formats.md:
- Rename 0x51 from reserved Keepalive to implemented Heartbeat
- Update Disconnect reason 0x07 to Heartbeat liveness timeout

testing/chaos/README.md:
- Add runner.log to output files
- Add Directed Outbound Configs subsection

testing/chaos/README.md

@@ -118,6 +118,15 @@ logging:
 When `ensure_connected` is true (default), the generator retries up to
 50 times to produce a connected graph.
 
+### Directed Outbound Configs
+
+The config generator assigns each edge to exactly one node for outbound
+connection using a BFS spanning tree rooted at the lowest node ID. Tree
+edges are assigned parent-to-child; non-tree edges are assigned from the
+lower node ID to the higher. This eliminates the dual-connect race
+condition where both sides initiate simultaneously, and creates a clear
+"owning side" for each link — relevant for auto-reconnect testing.
+
 ## Output
 
 Results written to `sim-results/` (configurable via
@@ -125,6 +134,7 @@ Results written to `sim-results/` (configurable via
 
 - `analysis.txt` -- Summary: panics, errors, sessions, metrics
 - `metadata.txt` -- Seed, node count, edges, adjacency list
+- `runner.log` -- Orchestration events (topology, netem, churn, traffic) with timestamps
 - `fips-node-nXX.log` -- Per-node log output
 
 Exit code 0 on success, 2 if panics detected.