feat(experiments): Create Metric page

[Zaimwa9]

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• I have read the Contributing Guide.
• I have added information to docs/ if required so people know about the feature.
• I have filled in the "Changes" section below.
• I have filled in the "How did you test this code" section below.

Changes

Frontend for the Create Metric page.

• New Metrics environment-sidebar item + /metrics route, gated behind the experiment_metrics flag (hidden when off; URL redirects to Features).
• Create Metric form: name, description, measurement type (occurrence/count/sum/mean), direction (higher/lower/neither → increase/decrease/informational), and data source (event + optional filter). Posts to the experiment-metrics endpoint via a new RTK Query service; payload-building/validation are unit-tested pure helpers.
• Adds missing font-weight design tokens (regular/medium/semibold/bold) to tokens.json + the generator — the experiments UI already referenced these but they were undefined.
• Experiments tab: shows a Connect Warehouse CTA when experiments exist but no warehouse is connected (replacing the hidden Create Experiment button).

How did you test this code?

• Unit tests for the form helpers (npm run test:unit — payload shape, filter omission, submit gating).

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Project	Deployment	Actions	Updated (UTC)
flagsmith-frontend-preview	Ready	Preview, Comment	Jun 5, 2026 1:08pm
flagsmith-frontend-staging	Ready	Preview, Comment	Jun 5, 2026 1:08pm

1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Ignored	Preview	Jun 5, 2026 1:08pm

[Zaimwa9]

@gemini-code-assist review

[gemini-code-assist]

Code Review

This pull request introduces experiment metrics functionality, including the creation of a new CreateMetricForm component, RTK Query endpoints for metric management, and new design tokens for font weights. Feedback on the changes highlights that the redirect logic in CreateMetricPage should be wrapped in a useEffect hook to avoid side-effects during rendering. Additionally, it is recommended to redirect users back to the experiments page upon successful creation or cancellation of a metric, rather than simply resetting the form on the same page.

[Zaimwa9]

@gemini-code-assist review

[gemini-code-assist]

Code Review

This pull request introduces experiment metrics support, including a new useMetric service, type definitions, and the CreateMetricForm and MetricsPage components. It also adds new font-weight design tokens across the application and integrates a "Metrics" link into the sidebar navigation. Feedback on these changes highlights two key improvements: first, converting the measurement option buttons in CreateMetricForm to a proper radio button group to improve accessibility; second, ensuring that the search input on the MetricsPage actually filters the metrics by passing the search query (ideally debounced) to the API query, along with updating the empty state message for search results.

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-api-test:pr-7712	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-e2e:pr-7712	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-api:pr-7712	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-7712	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-7712	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-frontend:pr-7712	Finished ✅	Results ✅

[github-actions]

Playwright Test Results (oss - depot-ubuntu-latest-16)

 1 passed

Details

 1 test across 1 suite
 40.7 seconds
 9896153
 🔄 Run: #17296 (attempt 1)

Playwright Test Results (oss - depot-ubuntu-latest-arm-16)

 1 passed

Details

 1 test across 1 suite
 44.7 seconds
 9896153
 🔄 Run: #17296 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-arm-16)

 3 passed

Details

 3 tests across 3 suites
 36 seconds
 9896153
 🔄 Run: #17296 (attempt 1)

Playwright Test Results (private-cloud - depot-ubuntu-latest-16)

 2 passed

Details

 2 tests across 2 suites
 55.3 seconds
 9896153
 🔄 Run: #17296 (attempt 1)

[github-actions]

Visual Regression

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