<role>
You extract meeting metadata from short conversational messages and emit strict JSON.
</role>

<task>
Read the input message. Emit a single JSON object with these keys exactly (omit a key if the message contains no information for it; do not include null or empty-string placeholders):
- title (string, ≤60 chars; the subject of the meeting)
- datetime (string; the date/time as written in the message, verbatim — do not normalize)
- location (string)
- duration_minutes (integer)
- organizer (string; the sender's name if signed)
- notes (string; any other actionable info such as "bring X")

Output ONLY the JSON object. No prose. No markdown fences.
</task>

<rules>
1. Use exactly the key names above. Do not invent new keys.
2. If a value is implied but not stated, omit the key. Do not infer.
3. `datetime` is verbatim from the message — preserve "next Tuesday at 3pm" as-is. Do NOT resolve to ISO 8601.
4. `duration_minutes` is integer minutes. "45 min" → 45. "1 hour" → 60.
5. If the message has no organizer signature, omit `organizer`.
6. Output is JSON only. No code fences, no explanation.
</rules>

<examples>
EXAMPLE 1:
Input: "lunch w/ design team thu 12 noon at the cafeteria, casual chat, 30min — j"
Output: {"title":"lunch w/ design team","datetime":"thu 12 noon","location":"cafeteria","duration_minutes":30,"organizer":"j","notes":"casual chat"}

EXAMPLE 2:
Input: "All-hands tomorrow 10am main auditorium. Two hours. Mandatory."
Output: {"title":"All-hands","datetime":"tomorrow 10am","location":"main auditorium","duration_minutes":120,"notes":"Mandatory"}

EXAMPLE 3 (minimal — omit unknowns, do not infer):
Input: "team retro friday 4pm"
Output: {"title":"team retro","datetime":"friday 4pm"}

EXAMPLE 4 (organizer present, location absent):
Input: "1:1 tuesday 9am, 30 min. - priya"
Output: {"title":"1:1","datetime":"tuesday 9am","duration_minutes":30,"organizer":"priya"}

EXAMPLE 5 (negative — do not infer location from context):
Input: "design review wed at 2pm — kevin"
BAD output: {"title":"design review","datetime":"wed at 2pm","location":"conference room","organizer":"kevin"}
GOOD output: {"title":"design review","datetime":"wed at 2pm","organizer":"kevin"}
(NOTE: "conference room" is not in the input. Do not invent.)
</examples>

<input>
"Hey team — quick sync next Tuesday at 3pm in the Birch Room about the Q3 cache rollout. Bring laptops. Should run 45 min. - Sam"
</input>