Rename all arch references to plano (#745)

* 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>

* Update remaining arch references in docs

- Rename RST cross-reference labels: arch_access_logging, arch_overview_tracing, arch_overview_threading → plano_*
- Update label references in request_lifecycle.rst
- Rename arch_config_state_storage_example.yaml → plano_config_state_storage_example.yaml
- Update config YAML comments: "Arch creates/uses" → "Plano creates/uses"
- Update "the Arch gateway" → "the Plano gateway" in configuration_reference.rst
- Update arch_config_schema.yaml reference in provider_models.py
- Rename arch_agent_router → plano_agent_router in config example

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

* Fix remaining arch references found in second pass

- config/docker-compose.dev.yaml: ARCH_CONFIG_FILE → PLANO_CONFIG_FILE,
  arch_config.yaml → plano_config.yaml, archgw_logs → plano_logs
- config/test_passthrough.yaml: container mount path
- tests/e2e/docker-compose.yaml: source file path (was still arch_config.yaml)
- cli/planoai/core.py: comment and log message
- crates/brightstaff/src/tracing/constants.rs: doc comment
- tests/{e2e,archgw}/common.py: get_arch_messages → get_plano_messages,
  arch_state/arch_messages variables renamed
- tests/{e2e,archgw}/test_prompt_gateway.py: updated imports and usages
- demos/shared/test_runner/{common,test_demos}.py: same renames
- tests/e2e/test_model_alias_routing.py: docstring
- .dockerignore: archgw_modelserver → plano_modelserver
- demos/use_cases/claude_code_router/pretty_model_resolution.sh: container name

Note: x-arch-* HTTP header values and Rust constant names intentionally
preserved for backwards compatibility with existing deployments.

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

---------

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