feat(llm): extract adapter layer for standalone llm-connect package (S1+S2)

Stage 1 — Decouple:
- Move RunConfig + LLMResponse to markitect/llm/models.py (canonical)
- Move LLMAdapter + Mock/ErrorLLMAdapter to markitect/llm/adapter.py
- markitect/prompts/execution/models.py and llm_adapter.py become re-export shims
- All 4 adapters + factory.py updated to import from markitect.llm.*
- Parameterize app_name in toml_config.py (resolve_llm, get_default_layers,
  get_preference_layers): paths and env var now derived from app_name arg
- Add tests/test_llm_isolation.py: 7 isolation + backward-compat tests

Stage 2 — Extract:
- Standalone llm-connect package created at ~/llm-connect/
- All 18 llm files copied; markitect.* imports replaced with llm_connect.*
- LLMError base inlined in llm_connect/exceptions.py (no markitect dep)
- llm-connect installed into markitect-venv; declared in pyproject.toml

Smoke test: markitect llm-check succeeds (live Gemini API call).
Backward compat: markitect.prompts.execution.{models,llm_adapter} still work.

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

markitect/llm/toml_config.py

@@ -28,13 +28,28 @@ from markitect.llm.config import find_project_root
 
 HARDCODED_PROVIDER = "gemini"
 HARDCODED_MODEL = "gemini-2.5-flash"
-MODEL_ENV_VAR = "MARKITECT_HELPER_MODEL"
 
+# Default (markitect) values kept for backward compatibility.
+MODEL_ENV_VAR = "MARKITECT_HELPER_MODEL"
 USER_CONFIG_DIR = Path.home() / ".config" / "markitect"
 USER_CONFIG_PATH = USER_CONFIG_DIR / "config.toml"
 DIR_CONFIG_NAME = ".markitect.toml"
 
 
+# ── App-name helpers ───────────────────────────────────────────────────────
+
+def _model_env_var(app_name: str) -> str:
+    return f"{app_name.upper()}_HELPER_MODEL"
+
+
+def _user_config_path(app_name: str) -> Path:
+    return Path.home() / ".config" / app_name / "config.toml"
+
+
+def _dir_config_name(app_name: str) -> str:
+    return f".{app_name}.toml"
+
+
 # ── Data classes ──────────────────────────────────────────────────────────
 
 @dataclass
@@ -114,11 +129,11 @@ def _clear_llm_section(path: Path, section: str) -> bool:
 
 # ── Directory config path helper ─────────────────────────────────────────
 
-def _dir_config_path() -> Optional[Path]:
+def _dir_config_path(app_name: str = "markitect") -> Optional[Path]:
     root = find_project_root()
     if root is None:
         return None
-    return root / DIR_CONFIG_NAME
+    return root / _dir_config_name(app_name)
 
 
 # ── Resolution ───────────────────────────────────────────────────────────
@@ -126,13 +141,23 @@ def _dir_config_path() -> Optional[Path]:
 def resolve_llm(
     cli_provider: Optional[str] = None,
     cli_model: Optional[str] = None,
+    app_name: str = "markitect",
 ) -> ResolvedLLM:
     """Walk the 7-level priority chain and return a fully resolved config.
 
     Provider and model are resolved independently — each takes the value
     from its highest-priority source.
+
+    Args:
+        cli_provider: Provider override from CLI.
+        cli_model: Model override from CLI.
+        app_name: Application name used to derive config paths and the
+            env-var prefix (e.g. ``"railiance"`` → ``RAILIANCE_HELPER_MODEL``
+            and ``~/.config/railiance/config.toml``).
     """
-    dir_path = _dir_config_path()
+    dir_path = _dir_config_path(app_name)
+    user_cfg = _user_config_path(app_name)
+    env_var = _model_env_var(app_name)
 
     # Build the layers (highest priority first).
     layers: list[tuple[str, LLMLayer]] = []
@@ -141,13 +166,13 @@ def resolve_llm(
     layers.append(("CLI flag", LLMLayer(provider=cli_provider, model=cli_model)))
 
     # 2. Env var (model only)
-    env_model = os.environ.get(MODEL_ENV_VAR) or None
-    layers.append(("env MARKITECT_HELPER_MODEL", LLMLayer(model=env_model)))
+    env_model = os.environ.get(env_var) or None
+    layers.append((f"env {env_var}", LLMLayer(model=env_model)))
 
     # 3. User preference
     layers.append((
         "user preference",
-        _read_llm_section(USER_CONFIG_PATH, "preference"),
+        _read_llm_section(user_cfg, "preference"),
     ))
 
     # 4. Directory preference
@@ -167,7 +192,7 @@ def resolve_llm(
     # 6. User default
     layers.append((
         "user default",
-        _read_llm_section(USER_CONFIG_PATH, "default"),
+        _read_llm_section(user_cfg, "default"),
     ))
 
     # 7. Hardcoded
@@ -199,20 +224,22 @@ def resolve_llm(
     )
 
 
-def get_default_layers() -> list[tuple[str, LLMLayer]]:
+def get_default_layers(app_name: str = "markitect") -> list[tuple[str, LLMLayer]]:
     """Return only the default layers for display."""
-    dir_path = _dir_config_path()
+    dir_path = _dir_config_path(app_name)
+    user_cfg = _user_config_path(app_name)
+    dir_cfg_name = _dir_config_name(app_name)
     layers: list[tuple[str, LLMLayer]] = []
 
     if dir_path:
         layers.append((
-            f"Directory default ({DIR_CONFIG_NAME})",
+            f"Directory default ({dir_cfg_name})",
             _read_llm_section(dir_path, "default"),
         ))
 
     layers.append((
-        f"User default ({USER_CONFIG_PATH})",
-        _read_llm_section(USER_CONFIG_PATH, "default"),
+        f"User default ({user_cfg})",
+        _read_llm_section(user_cfg, "default"),
     ))
 
     layers.append((
@@ -223,19 +250,21 @@ def get_default_layers() -> list[tuple[str, LLMLayer]]:
     return layers
 
 
-def get_preference_layers() -> list[tuple[str, LLMLayer]]:
+def get_preference_layers(app_name: str = "markitect") -> list[tuple[str, LLMLayer]]:
     """Return only the preference layers for display."""
-    dir_path = _dir_config_path()
+    dir_path = _dir_config_path(app_name)
+    user_cfg = _user_config_path(app_name)
+    dir_cfg_name = _dir_config_name(app_name)
     layers: list[tuple[str, LLMLayer]] = []
 
     layers.append((
-        f"User preference ({USER_CONFIG_PATH})",
-        _read_llm_section(USER_CONFIG_PATH, "preference"),
+        f"User preference ({user_cfg})",
+        _read_llm_section(user_cfg, "preference"),
     ))
 
     if dir_path:
         layers.append((
-            f"Directory preference ({DIR_CONFIG_NAME})",
+            f"Directory preference ({dir_cfg_name})",
             _read_llm_section(dir_path, "preference"),
         ))