docs: replace AGENTS.md with a repo-specific CLAUDE.md

One agent doc per repo, and it is CLAUDE.md. Written fresh rather than
reformatted. PHILOSOPHY.md linked to the old file, so that pointer moves
with it, and its standing requirement to be read before working here is
carried forward rather than lost in the rewrite.

Two claims did not survive verification. The app is published on 9999,
not the tower:8092 the old file gave, and it pointed at portainer-core
for full-stack documentation -- that repo is deprecated and must not be
used as a source of infra facts.

Establishing what is live needs a different method here: there is no
sys.modules to read, since the container holds a compiled web build
rather than source. A transitive walk of import/export/part directives
from lib/main.dart found 8 of 132 files unreachable, and five of those
are exactly what runs in production. They are conditional-import targets
-- `import 'a.dart' if (dart.library.html) 'b.dart'` -- and a walk that
takes the first string misses the branch. Since this ships as Flutter
web, the _web half is live and the _stub/_native half is dormant. The
naive reading was not merely wrong but inverted.

Of the three genuinely unreferenced files, stack_model.dart is imported
only by its own test, so the suite is green and vouches for a model the
app never uses. permission_gate.dart sits next to an unimplemented auth
redesign and is recorded as undetermined rather than dead.

Co-Authored-By: Claude <noreply@anthropic.com>

PHILOSOPHY.md

@@ -109,7 +109,7 @@ The butler (backend) runs the household. The UI opens the door.
 
 **Related Documents**:
 - **README.md**: Project setup and operational details
-- **AGENTS.md**: LLM agent development guidelines
+- **CLAUDE.md**: LLM agent development guidelines
 - **PLAN.md**: Implementation roadmap and phases
 
 ---