fix: multi-user distillation + datetime in context + session log labels

Distillation was silently operating on scott/inara for all users due to
ContextVar defaults. All three distill endpoints now require ?user=&persona=
query params and validate them via persona.validate(). Memory distiller
signatures changed from Optional to required positional args — no more
global settings fallback. Scheduler now iterates all users/personas instead
of hardcoding the primary user.

- context_loader: inject current date/time as first system prompt section
- session_logger: use get_user()/get_persona() from context instead of
  settings globals so Holly/Brian sessions show correct speaker labels
- memory_distiller: system prompts now reference u.title()/p.title()
  instead of settings.user_name/settings.agent_name
- distill router: Query(...) enforces params; _resolve() validates persona
- scheduler: _all_personas() helper iterates every user/persona for distill
- app.js: runDistill() now appends ?user=&persona= via _fileParams

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

cortex/routers/distill.py

@@ -5,14 +5,29 @@ Manual memory distillation endpoints.
   POST /distill/mid    — summarize short   → MEMORY_MID.md   (LLM)
   POST /distill/long   — integrate mid     → MEMORY_LONG.md  (LLM)
   POST /distill/all    — run all three in sequence
+
+All endpoints require ?user=<username>&persona=<name> query params so distillation
+targets the correct persona. Without them, the request is rejected (no silent fallback
+to server defaults — that caused wrong-user distillation in a multi-user setup).
 """
-from fastapi import APIRouter
+from fastapi import APIRouter, HTTPException, Query
 from memory_distiller import distill_short, distill_mid, distill_long
+from persona import validate as validate_persona, set_context
 import scheduler
 
 router = APIRouter(prefix="/distill")
 
 
+def _resolve(user: str, persona: str) -> tuple[str, str]:
+    """Validate and set persona context. Raises 404 if the persona doesn't exist."""
+    try:
+        u, p = validate_persona(user, persona)
+    except Exception:
+        raise HTTPException(status_code=404, detail=f"Persona not found: {user}/{persona}")
+    set_context(u, p)
+    return u, p
+
+
 @router.get("/status")
 async def distill_status() -> dict:
     """Show auto-distillation schedule and next run times."""
@@ -29,29 +44,45 @@ async def distill_status() -> dict:
 
 
 @router.post("/short")
-async def do_distill_short() -> dict:
-    return {"ok": True, **distill_short()}
+async def do_distill_short(
+    user: str = Query(...),
+    persona: str = Query(...),
+) -> dict:
+    u, p = _resolve(user, persona)
+    return {"ok": True, **distill_short(u, p)}
 
 
 @router.post("/mid")
-async def do_distill_mid() -> dict:
-    result = await distill_mid()
+async def do_distill_mid(
+    user: str = Query(...),
+    persona: str = Query(...),
+) -> dict:
+    u, p = _resolve(user, persona)
+    result = await distill_mid(u, p)
     return {"ok": "error" not in result, **result}
 
 
 @router.post("/long")
-async def do_distill_long() -> dict:
-    result = await distill_long()
+async def do_distill_long(
+    user: str = Query(...),
+    persona: str = Query(...),
+) -> dict:
+    u, p = _resolve(user, persona)
+    result = await distill_long(u, p)
     return {"ok": "error" not in result, **result}
 
 
 @router.post("/all")
-async def do_distill_all() -> dict:
-    short_result = distill_short()
-    mid_result = await distill_mid()
+async def do_distill_all(
+    user: str = Query(...),
+    persona: str = Query(...),
+) -> dict:
+    u, p = _resolve(user, persona)
+    short_result = distill_short(u, p)
+    mid_result = await distill_mid(u, p)
     if "error" in mid_result:
         return {"ok": False, "short": short_result, "mid": mid_result}
-    long_result = await distill_long()
+    long_result = await distill_long(u, p)
     return {
         "ok": "error" not in long_result,
         "short": short_result,