feat(agents): manifest plumbing + GET /agents/registry (ADR-0014 step 3)

Each agent now exports a module-level MANIFEST declaring id, version,
pref_schema, required_consents, ttl_sec, and silenced_in_contexts. The
registry surfaces both the agent and its manifest, and rejects on
mismatch so the two cannot drift.

ml/serving exposes GET /agents/registry; services/api proxies it as
GET /api/agents/registry with a 60s in-process cache so admin pageviews
don't hammer upstream. Failures aren't cached.

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

ml/agents/time_of_day.py

@@ -1,15 +1,43 @@
 from __future__ import annotations
 from typing import ClassVar
 from .base import BaseAgent, AgentInput, AgentOutput
+from .manifest import AgentManifest
 
 _DOW_NAMES = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"]
 
 
+MANIFEST = AgentManifest(
+    id="time-of-day",
+    version="1.0.0",
+    description="Frames the current moment relative to the user's productive peak and quiet hours.",
+    pref_schema={
+        "type": "object",
+        "additionalProperties": False,
+        "properties": {
+            "quiet_start": {
+                "type": "string",
+                "pattern": "^([01][0-9]|2[0-3]):[0-5][0-9]$",
+                "description": "HH:MM start of quiet hours (24h, user's local TZ).",
+            },
+            "quiet_end": {
+                "type": "string",
+                "pattern": "^([01][0-9]|2[0-3]):[0-5][0-9]$",
+                "description": "HH:MM end of quiet hours.",
+            },
+        },
+    },
+    context_schema=["profile.features"],
+    required_consents=["data:core", "agent:time-of-day"],
+    output_contract={"type": "snippet", "format": "free_text"},
+    ttl_sec=900,
+)
+
+
 class TimeOfDayAgent(BaseAgent):
     """Frames the current moment relative to the user's productive peak."""
-    agent_id: ClassVar[str] = "time-of-day"
-    ttl_seconds: ClassVar[int] = 900  # 15m — must stay current-hour accurate
-    version: ClassVar[str] = "1.0.0"
+    agent_id: ClassVar[str] = MANIFEST.id
+    ttl_seconds: ClassVar[int] = MANIFEST.ttl_sec
+    version: ClassVar[str] = MANIFEST.version
 
     def compute(self, inp: AgentInput) -> AgentOutput:
         hour = inp.now.hour