Rename all arch references to plano across the codebase

Complete rebrand from "Arch"/"archgw" to "Plano" including:
- Config files: arch_config_schema.yaml, workflow, demo configs
- Environment variables: ARCH_CONFIG_* → PLANO_CONFIG_*
- Python CLI: variables, functions, file paths, docker mounts
- Rust crates: config paths, log messages, metadata keys
- Docker/build: Dockerfile, supervisord, .dockerignore, .gitignore
- Docker Compose: volume mounts and env vars across all demos/tests
- GitHub workflows: job/step names
- Shell scripts: log messages
- Demos: Python code, READMEs, VS Code configs, Grafana dashboard
- Docs: RST includes, code comments, config references
- Package metadata: package.json, pyproject.toml, uv.lock

External URLs (docs.archgw.com, github.com/katanemo/archgw) left as-is.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/archgw/docker-compose.yaml

@@ -5,7 +5,7 @@ services:
       - "10000:10000"
       - "12000:12000"
     volumes:
-      - ./config.yaml:/app/arch_config.yaml
+      - ./config.yaml:/app/plano_config.yaml
       - /etc/ssl/cert.pem:/etc/ssl/cert.pem
     extra_hosts:
       - "host.docker.internal:host-gateway"

tests/archgw/pyproject.toml

@@ -1,7 +1,7 @@
 [project]
-name = "archgw_mock_tests"
+name = "plano_mock_tests"
 version = "0.0.1"
-description = "archgw mock tests"
+description = "plano mock tests"
 authors = [{name = "Katanemo Labs, Inc", email = "info@katanemo.com"}]
 license = {text = "Apache 2.0"}
 requires-python = ">=3.12"

tests/archgw/uv.lock

@@ -2,7 +2,7 @@ version = 1
 requires-python = ">=3.12"
 
 [[package]]
-name = "archgw-mock-tests"
+name = "plano-mock-tests"
 version = "0.0.1"
 source = { editable = "." }
 dependencies = [