Bug / behaviour tweak: Saturday “pop in” message is being escalated instead of handled as an appointment.

Context
- Channel: WhatsApp inbound
- Endpoint: /api/lia/inbound
- Customer: my test record (phone +447972194025)
- Conversation state before message:
  - stage: "12"
  - campaign: "TEST_12_PCP"
  - status: "active"
  - appointment_status: "INVITED" (time slots already offered earlier in the flow)

Inbound message that triggers the issue
"Hi could I pop in on Saturday to have a look at options"

Current backend response (from /api/lia/inbound):
{
  "conversation_id": "9a1c02d3-1b2f-4525-b004-866e493ccbd4",
  "mode": "AWAITING_MANAGER",
  "status": "active",
  "defer_until": null,
  "reply": "",
  "stage": "12"
}

So:
- mode = AWAITING_MANAGER
- reply = "" (empty)

Make is now correctly wired to **only call Twilio if length(reply) > 0**, so this correctly results in **no WhatsApp reply being sent**.

The problem is classification: this message is clearly “customer wants to visit on Saturday to look at options”, but it’s being treated as an escalation instead of part of the T3 appointment flow.

Desired behaviour
For messages like:
- "Hi could I pop in on Saturday?"
- "Can I come in on Saturday to have a look at options?"
- "Is a quick visit on Saturday ok?"

…when:
- appointment_status is NONE or INVITED
- status is active
- not DNC / not paused
- and we’re in a renewal context (EOT / TEST_12_PCP etc)

…please route them into the **T3 appointment flow**, not AWAITING_MANAGER.

Concretely, I’d expect something like:
- mode: APPOINTMENT_TIME_CHOICES (or APPOINTMENT_VAGUE → then offer two slots)
- reply: a message offering two clear time options and asking which suits them best
- appointment_status: remain INVITED until a specific time is chosen (as per current design)

Escalation to AWAITING_MANAGER should only happen when:
- it’s genuinely unclear or off-topic, or
- there’s a clear complaint / issue, or
- your existing escalation rules are triggered (e.g. CONFUSION_SECOND, customer_issue, etc.)

This particular sentence is a **clean “I want to visit” intent**, no complaint, no confusion.

Acceptance test
Once updated, this sequence should pass:

1) Outbound: LIA invites me and I reply “Hi could I pop in on Saturday to have a look at options”.
2) /api/lia/inbound returns something like:
   - mode: APPOINTMENT_TIME_CHOICES (or equivalent T3 appointment mode)
   - status: "active"
   - reply: a short, human message offering 2 time slots and asking which I prefer.
3) Make sends that reply to WhatsApp (because reply is non-empty).
4) No AWAITING_MANAGER / empty reply for this kind of “pop in on Saturday” message.

IMPORTANT: please keep the new post-booking guards and duplicate suppression you recently added (APPOINTMENT_CONFIRMED + POST_BOOKING_ACK logic). This change is only about initial “can I pop in on Saturday” intent being treated as appointment flow, not escalation.

Once this is done, tell me which mode/template key you’re using so I can share it with CPO for wording checks if needed.