Rewrite as current state rather than how it was decided

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013kj58Jugkic783b8ZrtTVZ

README.md

@@ -12,10 +12,8 @@ This file serves as the minimalist portal to other docs
 Everything needed to bring up a believable fake car on a workstation, so the rest
 of the project can be developed with no Jetson, no PCBs and no Z27AG present.
 
-One repo rather than one per fixture: they share the contract, they change
-together when a schema changes, and the whole point is to bring the fake
-environment up in a single step. Splitting them would make that an orchestration
-problem for no gain.
+All fixtures live here together: they share the contract, they change together
+when a schema changes, and the environment comes up in one step.
 
 - For implementation practice guidelines, refer to the [guidelines](docs/GUIDELINES.md);  
 - For implementation plans and history, refer to [them](docs/impl/);

docs/GUIDELINES.md

@@ -6,8 +6,9 @@ type: guidelines
 ## 1. Fixtures publish the real contract
 - A fixture emits the **real topic with the real payload schema**. `yukart/gnss/fix`
   from a replayed track must be indistinguishable, at the bus, from a real fix.  
-- A fixture that invents its own topic or shape is worse than no fixture: it defers
-  the integration work instead of removing it.
+- ⚠ **A fixture that invents its own topic or shape defers integration rather than
+  removing it** — the mismatch surfaces when the real source arrives, which is the
+  moment it is most expensive.
 
 ## 2. Do not reimplement our own services
 - Stub the **car** and the **hardware**. Never write a *separate* implementation of