Alerts on Web Vitals and Custom Measurements (INP) not being rendered

### Self-Hosted Version

25.9.0

### CPU Architecture

x86_64

### Docker Version

28.4.0

### Docker Compose Version

2.39.2

### Machine Specification

- [x] My system meets the minimum system requirements of Sentry

### Installation Type

Upgrade to 25.9.0

### Steps to Reproduce

1. Setup a frontend application with Sentry sdk (Tried both React and Vue)
2. Start reporting Web Vitals (Including Session Replays, Rage Clicks and INP in my case)
3. Setup an alert on Custom Measurement p75(INP)
- When INP > 300 for 5 minutes"
- Send an Email (Critical)

This is a kick starter project https://github.com/[MichelBitar99/sentry-frontend-performance-inp-issue](https://github.com/MichelBitar99/sentry-frontend-performance-inp-issue)
Make sure to create a .env with the following configs:

VITE_SENTRY_DSN=
VITE_SENTRY_TRACES_SAMPLE_RATE=1.0
VITE_SENTRY_INTERACTIONS_SAMPLE_RATE=1.0
VITE_SENTRY_REPLAY_SESSION_SAMPLE_RATE=1.0
VITE_SENTRY_REPLAY_ERROR_SAMPLE_RATE=1.0

### Expected Result

I expect when opening the alert instance to actually see the p75(inp) values, however they are showing as 'No Value' and not being rendered on the panel.
Although from the Web Vitals page, I can clearly see INP is being recorded properly, and the alert did detect issues.

### Actual Result

In the alert, where it got triggered, I cannot see the rendering of INP on the panel.
When hovering over the panel is shows as if the measurement was 0 even though Alert was triggered.
In the Transactions table, the INP shows as 'No Value'

### Event ID

_No response_

Start by reproducing the issue with the linked Sentry frontend kick-starter and the provided environment variables, then compare the alert instance and Transactions table with the Web Vitals page. Investigate why p75(INP) appears as “No Value” or 0 despite the alert triggering. Done means the alert panel and transaction view render the recorded INP measurement.

Written by the indexing model from the issue text.