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>

docs/source/concepts/prompt_target.rst

@@ -114,7 +114,7 @@ Example 1: Adjusting Retrieval
 
     User: What are the benefits of renewable energy?
     **[Plano]**: Check if there is an available <prompt_target> that can handle this user query.
-    **[Plano]**: Found "get_info_for_energy_source" prompt_target in arch_config.yaml. Forward prompt to the endpoint configured in "get_info_for_energy_source"
+    **[Plano]**: Found "get_info_for_energy_source" prompt_target in plano_config.yaml. Forward prompt to the endpoint configured in "get_info_for_energy_source"
     ...
     Assistant: Renewable energy reduces greenhouse gas emissions, lowers air pollution, and provides sustainable power sources like solar and wind.
 
@@ -130,13 +130,13 @@ Example 2: Switching Intent
 
     User: What are the symptoms of diabetes?
     **[Plano]**: Check if there is an available <prompt_target> that can handle this user query.
-    **[Plano]**: Found "diseases_symptoms" prompt_target in arch_config.yaml. Forward disease=diabeteres to "diseases_symptoms" prompt target
+    **[Plano]**: Found "diseases_symptoms" prompt_target in plano_config.yaml. Forward disease=diabeteres to "diseases_symptoms" prompt target
     ...
     Assistant: Common symptoms include frequent urination, excessive thirst, fatigue, and blurry vision.
 
     User: How is it diagnosed?
     **[Plano]**: New intent detected.
-    **[Plano]**: Found "disease_diagnoses" prompt_target in arch_config.yaml. Forward disease=diabeteres to "disease_diagnoses" prompt target
+    **[Plano]**: Found "disease_diagnoses" prompt_target in plano_config.yaml. Forward disease=diabeteres to "disease_diagnoses" prompt target
     ...
     Assistant: Diabetes is diagnosed through blood tests like fasting blood sugar, A1C, or an oral glucose tolerance test.
 
@@ -172,7 +172,7 @@ Once the prompt targets are configured as above, handle parameters across multi-
 Demo App
 --------
 
-For your convenience, we've built a `demo app <https://github.com/katanemo/archgw/tree/main/demos/samples_python/multi_turn_rag_agent>`_
+For your convenience, we've built a `demo app <https://github.com/katanemo/plano/tree/main/demos/samples_python/multi_turn_rag_agent>`_
 that you can test and modify locally for multi-turn RAG scenarios.
 
 .. figure:: ../build_with_plano/includes/multi_turn/mutli-turn-example.png