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/e2e/run_e2e_tests.sh

@@ -34,7 +34,7 @@ uv sync
 uv tool install .
 cd -
 
-log building docker image for arch gateway
+log building docker image for plano gateway
 log ======================================
 cd ../../
 planoai build
@@ -43,7 +43,7 @@ cd -
 # Once we build plano we have to install the dependencies again to a new virtual environment.
 uv sync
 
-log startup arch gateway with function calling demo
+log startup plano gateway with function calling demo
 cd ../../
 planoai down
 planoai up demos/samples_python/weather_forecast/config.yaml
@@ -53,11 +53,11 @@ log running e2e tests for prompt gateway
 log ====================================
 uv run pytest test_prompt_gateway.py
 
-log shutting down the arch gateway service for prompt_gateway demo
+log shutting down the plano gateway service for prompt_gateway demo
 log ===============================================================
 planoai down
 
-log startup arch gateway with model alias routing demo
+log startup plano gateway with model alias routing demo
 cd ../../
 planoai up demos/use_cases/model_alias_routing/config_with_aliases.yaml
 cd -
@@ -70,7 +70,7 @@ log running e2e tests for openai responses api client
 log ========================================
 uv run pytest test_openai_responses_api_client.py
 
-log startup arch gateway with state storage for openai responses api client demo
+log startup plano gateway with state storage for openai responses api client demo
 planoai down
 planoai up config_memory_state_v1_responses.yaml