### Steps to Reproduce:
1. Go to Helpdesk and create an SLA
2. Create a new Ticket
3. Use Studio to add the field `sla_reached`
4. Apply the SLA
5. Notice that the field is True

### Description of the issue/feature this PR addresses:
**Issue:** The `_compute_sla_reached` method in on `helpdesk_ticket.py` determines whether an SLA has been reached by checking if `exceeded_hours` is less than 0 on its `helpdesk.sla.status` records. Since every newly assigned SLA has a future deadline, `exceeded_hours` starts as negative (AKA <0), so the ticket is immediately flagged as `sla_reached = True` before any progress has been made. Conversely, a ticket that reaches its target stage after the deadline has `exceeded_hours >= 0`, so it's incorrectly flagged as `sla_reached = False` even though the SLA target was genuinely reached (it was just late).

**Solution:** Change the domain in `_compute_sla_reached` to check `reached_datetime != False` instead of `exceeded_hours < 0`, matching the field already listed in the method's `@api.depends` and the same field `_sla_reach()` sets when a ticket enters its target stage. This makes `sla_reached` reflect actual stage progression rather than a time-remaining calculation.

### Current behavior before PR: 
A newly created ticket with a pending SLA shows `sla_reached = True` and `sla_success = True` immediately upon creation, before the ticket has moved to any target stage. SImilarly, a ticket that reaches its target stage after the SLA deadline is incorrectly marked `sla_reached = False`.

### Desired behavior after PR: 
`sla_reached` is False on ticket creation and only becomes True once the ticket actually enters the SLA's target stage. Lateness continues to be tracked separately and correctly via `sla_reached_late`

opw-6361851

Forward-Port-Of: odoo/enterprise#126432

## Previous Behavior Before this Commit
1. When key and non‑key events were merged to build the final suggestion timeline, key events always took priority over AFK events, even when the key event was not “always active.” This caused AFK events to be incorrectly overridden.
2. During event normalization, certain events were lost entirely, resulting in important events not being counted.
3. When merging two event timelines, zero‑duration gaps were treated as valid, preventing proper merging of surrounding events.
4. ActivityWatch sometimes produced empty gaps instead of AFK events, causing breaks to go unrecorded.

## New Expected Behavior After this Commit
1. Events now follow the updated priority system: 
a. Always‑active key events 
b. Always‑active non‑key events 
c. Non‑key AFK events 
d. Other key events 
e. Other non‑key events
2. Events are now shortened or split so that the latest event always has priority, while minimizing unnecessary event removal.
3. Zero‑duration gaps are skipped when merging event lists.
4. Any gap larger than 3 minutes, between the first and last event and containing no events is automatically filled with an AFK event.

## Additional Notes
Because point 4 introduces additional AFK events, several tests were updated to reflect the new behavior.

task-[6455412](https://www.odoo.com/odoo/project/4105/tasks/6455412)