docs(rust): plan fixes — D173 quests are Rust's own missions, D174 title rules

D173: "Quests completed" (Wayfarer) counts the missions Rust's NPCs
already hand out; no quest plugin. uMod's catalogue names no mission
hook and CARBON.md lists none, so the detailed plan starts with a rig
spike: a framework hook if one exists at build time, else reading the
player's mission list at each tally flush, else a D168 helper patch.
D174 adopts §4.6's recommended title rules (best columns for kill
distance, weapon-class kills count every credited kill, killing-blow
credit for APC/heli, heals of others only).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

modules/rust/README.md

@@ -24,7 +24,7 @@ differ.
 for actually building `module-rust`. Everything else in this directory is copied from uMod; those two
 are written by this project and are where the phases, the settled decisions and the local test rig are
 recorded. [`PLAN_FIXES.md`](PLAN_FIXES.md) is its companion: the first player walk's fixes and decisions
-D159–D172, all to land before the Module-Rust cutover.
+D159–D174, all to land before the Module-Rust cutover.
 
 > **This is a mirror, not a specification we own.** uMod is upstream and wins any disagreement; the
 > point of copying it is availability and grep-ability, not authority. Nothing here may be cited as a