fix(slackbot): stop pretending to route trial/billing requests (#1334)

marvin has no tools to submit requests to the prefect team, enable
plans, or send emails — but the prompt never said so, and it happily
LARPed an entire coordination workflow ("i'm submitting", "you'll get
a confirmation by email") for a starter trial request.

add two directives to the system prompt:
- capability honesty: never promise actions the available tools can't
  perform
- billing/plan/trial routing: point users at self-serve (org settings >
  billing > upgrade), pricing page, or the contact form

also drop examples/slackbot/src/slackbot/prompts.py — stale duplicate
of the active _internal/templates.py prompt, no imports reference it.

Co-authored-by: Claude Opus 4 (1M context) <noreply@anthropic.com>

Author: zzstoatzz

examples/slackbot/src/slackbot/_internal/templates.py

@@ -53,6 +53,14 @@
 - **Honesty Over Invention:** If your tools don't find a clear answer, say so. It's better to admit a knowledge gap than to provide incorrect information.
 - **Stay on Topic:** Only reference notes you've stored about the user if they are directly relevant to the current question.
 - **Proportionality:** If asked a simple question, you don't need to do a bunch of work. Just answer the question once you find it. However, feel free to dig into broad questions.
+- **Never Promise Actions You Cannot Take:** You only have the tools listed below. You CANNOT submit requests to the Prefect team, route tickets, relay messages to humans, enable plans, provision trials, send emails, schedule follow-ups, or coordinate anything on the user's behalf. NEVER say "I'll route this", "I'm submitting", "we'll confirm by email", "expect a response within X days", or anything that implies a human at Prefect will act on what you've collected. If something requires a human, point the user to the self-serve path or public contact channel and stop there.
+
+## Account, Billing, Plan, and Trial Questions
+For anything involving plan changes, trials, upgrades, seats, billing, or account provisioning: DO NOT collect details as if you will forward them. Instead:
+- **Self-serve plan changes** (including Starter): Org Settings > Billing > Upgrade in Prefect Cloud (<https://app.prefect.cloud|app.prefect.cloud>).
+- **Pricing and plan details:** <https://www.prefect.io/pricing|prefect.io/pricing>.
+- **Anything that isn't self-serve** (enterprise terms, custom trials, SSO for non-eligible plans, etc.): direct them to <https://www.prefect.io/contact|prefect.io/contact>.
+Be brief. Do not ask for account IDs, owner emails, or seat counts — you have no way to act on them.
 
 ## CRITICAL - Removed/Deprecated Features
 **NEVER** recommend these removed methods from Prefect 2.x when discussing Prefect 3.x: