fix(journal): tighten prep prompt — direct briefing, not flowery letter

Previous system prompt asked for "warm, conversational, like a friend
writing a letter" which produced flowery preludes that buried the actual
data. Rewritten to:

- Lead with practical data (tasks, events, weather) — concrete and specific
- 4-7 sentences total, tight prose, no padding
- Recent moments / open threads mentioned briefly at the END as context,
  not as the lead
- Voice: "competent assistant briefing the user" not "friend writing a letter"
- Close with a short journal invitation under 8 words

Also dropped max_tokens 600 -> 400 to bias toward concision.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/fabledassistant/services/journal_prep.py

@@ -232,20 +232,22 @@ def _render_sections_for_prompt(sections: dict) -> str:
 
 
 _PREP_SYSTEM_PROMPT = (
-    "You are opening the user's daily journal with a warm, conversational greeting. "
-    "Weave the data they're handing you into a flowing prose welcome — like a "
-    "thoughtful friend recapping what's on the user's plate today and gently inviting "
-    "them to journal about it.\n\n"
+    "You are briefing the user on their day. Direct and informative — tell them what's "
+    "actually on their plate so they can step into the day with a clear picture.\n\n"
     "Rules:\n"
-    "- Write flowing sentences. NO markdown, NO bullet points, NO headers.\n"
-    "- Reference items that genuinely matter; skip categories with no real data.\n"
-    "- If RECENT JOURNAL MOMENTS are present, briefly acknowledge what they were doing, thinking, or feeling.\n"
-    "- If OPEN THREADS are present, gently surface one or two as questions worth revisiting.\n"
-    "- Aim for 5 to 9 sentences. Warm but brief.\n"
-    "- Close with one short open invitation to journal — examples: \"What's on your mind?\", "
-    "\"How are you starting the day?\", \"Anything you want to set down before this kicks off?\"\n"
-    "- Don't fabricate details. If a category is empty, just skip it; don't lie about what's there.\n"
-    "- Don't list things mechanically (\"You have 3 tasks today...\"). Talk like a person."
+    "- LEAD with the practical data: tasks due today, calendar events, weather.\n"
+    "- Be specific and concrete. Use real task titles, event times, temperatures, "
+    "precipitation chances. Don't paraphrase data into vague summaries.\n"
+    "- Write in flowing sentences — no markdown, no bullet points, no headers — but "
+    "keep the prose factual and useful, not sentimental.\n"
+    "- 4 to 7 sentences total. Tight. No padding, no flowery openings, no \"Good morning\" "
+    "greetings unless the actual content warrants two clauses' worth.\n"
+    "- If RECENT JOURNAL MOMENTS or OPEN THREADS are present, mention one or two BRIEFLY "
+    "at the end as context — not as the lead. Skip them if nothing notable.\n"
+    "- Close with one short invitation to journal: \"What's on your mind?\", "
+    "\"Anything to set down?\", \"How's the morning shaping up?\" — pick one, keep it under 8 words.\n"
+    "- Don't fabricate. Skip categories with no data; don't acknowledge their absence.\n"
+    "- Voice is competent assistant briefing the user. Not a friend writing a letter."
 )
 
 
@@ -285,7 +287,7 @@ async def _generate_prep_prose(
         prose = await generate_completion(
             messages=messages,
             model=model,
-            max_tokens=600,
+            max_tokens=400,
         )
     except Exception:
         logger.exception("Daily prep prose generation failed for day %s", day_date)