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>

cli/planoai/docker_cli.py

@@ -41,7 +41,7 @@ def docker_remove_container(container: str) -> str:
 
 
 def docker_start_plano_detached(
-    arch_config_file: str,
+    plano_config_file: str,
     env: dict,
     gateway_ports: list[int],
 ) -> str:
@@ -58,7 +58,7 @@ def docker_start_plano_detached(
     port_mappings_args = [item for port in port_mappings for item in ("-p", port)]
 
     volume_mappings = [
-        f"{arch_config_file}:/app/arch_config.yaml:ro",
+        f"{plano_config_file}:/app/plano_config.yaml:ro",
     ]
     volume_mappings_args = [
         item for volume in volume_mappings for item in ("-v", volume)
@@ -115,7 +115,7 @@ def stream_gateway_logs(follow, service="plano"):
         log.info(f"Failed to stream logs: {str(e)}")
 
 
-def docker_validate_plano_schema(arch_config_file):
+def docker_validate_plano_schema(plano_config_file):
     import os
 
     env = os.environ.copy()
@@ -129,7 +129,7 @@ def docker_validate_plano_schema(arch_config_file):
             "--rm",
             *env_args,
             "-v",
-            f"{arch_config_file}:/app/arch_config.yaml:ro",
+            f"{plano_config_file}:/app/plano_config.yaml:ro",
             "--entrypoint",
             "python",
             PLANO_DOCKER_IMAGE,