feat(webui): worker registry and configuration schema (Closes #798)

Add the declarative worker registry that epic #797 makes the source of
truth for the scheduled multi-LLM worker fleet.

Providers and configured workers are modelled as separate entities so a
provider can be listed with no worker configured, and so provider facts
are not copied into every worker record. A worker records provider,
model, project, role, namespace, profile, workflow, schedule, timeout,
enabled state, and scheduler metadata.

Validation fails closed: unknown fields are refused rather than ignored,
so a typo cannot silently disable a timeout; a worker naming an
undeclared provider is rejected; worker ids, provider ids, and
LaunchAgent labels must be unique.

Persistence is atomic (temp file in the same directory, fsync, replace).
Every superseded document is retained as a numbered revision, and
rollback republishes a chosen revision as a new head, so history stays
append-only and a rollback is itself reversible.

The credential-rejection guard is extracted to webui/registry_safety.py
so both registries share one implementation instead of two copies of a
security check; project_registry.py keeps identical behaviour.

Scope: data model, validation, persistence only. No routes, scheduler,
process control, or provider probing - those are #799/#800/#804/#805.
The workers array ships empty because populating it is #808.

Tests: tests/test_webui_worker_registry.py, 44 cases.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

webui/project_registry.py

@@ -8,27 +8,7 @@ from dataclasses import dataclass
 from pathlib import Path
 from typing import Any
 
-_FORBIDDEN_EXACT_KEYS = frozenset({
-    "token",
-    "password",
-    "secret",
-    "credential",
-    "auth",
-    "api_key",
-    "api-key",
-})
-_FORBIDDEN_KEY_PREFIXES = ("auth_", "api_key_", "api-key_")
-_FORBIDDEN_KEY_SUFFIXES = ("_token", "_secret", "_password", "_credential", "_auth")
-
-
-def _is_forbidden_key(key: str) -> bool:
-    lowered = key.lower()
-    if lowered in _FORBIDDEN_EXACT_KEYS:
-        return True
-    return (
-        lowered.startswith(_FORBIDDEN_KEY_PREFIXES)
-        or lowered.endswith(_FORBIDDEN_KEY_SUFFIXES)
-    )
+from webui.registry_safety import reject_credential_keys as _reject_credential_keys
 
 _REQUIRED_PROJECT_FIELDS = (
     "id",
@@ -79,18 +59,6 @@ def default_registry_path() -> Path:
     return (Path(__file__).resolve().parent / "data" / "projects.registry.json").resolve()
 
 
-def _reject_credential_keys(obj: Any, *, path: str = "") -> None:
-    if isinstance(obj, dict):
-        for key, value in obj.items():
-            key_path = f"{path}.{key}" if path else key
-            if _is_forbidden_key(key):
-                raise ValueError(f"registry must not store credentials ({key_path})")
-            _reject_credential_keys(value, path=key_path)
-    elif isinstance(obj, list):
-        for index, item in enumerate(obj):
-            _reject_credential_keys(item, path=f"{path}[{index}]")
-
-
 def _parse_onboarding(raw: list[dict[str, Any]] | None) -> tuple[OnboardingStep, ...]:
     if not raw:
         return ()