[mqtt branch] tests/test_ruleset_shape.lua is broken

**Status: needs triage**
**Affects:** mqtt branch (dev tooling, not gameplay)

## Symptom
`luajit tests/test_ruleset_shape.lua test` fails on the mqtt branch before reaching any assertions:

```
The system cannot find the path specified.
tests/test_ruleset_shape.lua:173: bad argument #1 to 'pairs' (table expected, got nil)
in function 'sorted_keys' (called from extract_all_shapes, line 248)
```

The "system cannot find the path specified" lines suggest a shell/path incompatibility (observed on Windows) before the nil-table failure. The rest of the suite (rlog, serialization) runs fine on the same setup, so this is specific to how this test discovers/loads ruleset files. Not yet diagnosed whether it's Windows-only or broken for everyone on this branch.

Run `luajit tests/test_ruleset_shape.lua test` on the mqtt branch, first reproducing the Windows failure if available. Read tests/test_ruleset_shape.lua around sorted_keys at line 173 and extract_all_shapes at line 248, then trace how the test discovers and loads ruleset files. Done means the test reaches its assertions and passes, with the shell/path behavior understood across the affected environments.

Written by the indexing model from the issue text.