docs: Good Fences Make Good Agents (design story + IBIS)

The story behind good-fences: lend a governed mower over the fence to a
neighbor whose tenants are model-written code, with the design IBIS
worked out so far. Previously an untracked note at the workspace root.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

good-fences/docs/lend-the-mower.md

@@ -1,6 +1,6 @@
 # Lend the mower
 
-The journey from [Good Fences Make Good Agents](../../../a2030.md): I lend
+The journey from [Good Fences Make Good Agents](../../docs/good-fences-make-good-agents.md): I lend
 my neighbor a governed mower; the neighbor's tenant, a little tipsy,
 pushes it until the fence stops it. The design decisions behind each actor are in that
 doc's Design IBIS (numbers in parentheses below).