Fix edit list modal population for legacy list types

[zackcl]

Resolves #3285

Some list responses use lowercase individual or segment values, while the Edit List modal expects their canonical casing, leaving the Type and Values fields empty.

Changes

• Normalize built-in Individual and Segment list types across frontend and backend write paths.
• Correctly populate edit forms for lists with lowercase standard types.
• Populate Segment list forms with the referenced public segment instead of the private wrapper.
• Preserve context-specific group types and count-only member loading.
• Validate Feature Flag list types and add focused regression coverage.

[Copilot]

Pull request overview

Fixes legacy list editing by canonicalizing built-in list types and correctly populating modal values.

Changes:

• Adds shared normalization for Individual and Segment.
• Correctly loads members and referenced public segments during editing.
• Validates write paths and adds regression tests.

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/types/src/index.ts	Exports normalization utilities.
packages/types/src/Experiment/enums.ts	Defines canonical list types and normalization.
packages/frontend/.../common-details-participant-list-table.component.ts	Normalizes list-type display and checks.
packages/frontend/.../common-details-participant-list-table.component.html	Uses normalized segment detection.
packages/frontend/.../upsert-private-segment-list-modal.component.ts	Populates edit forms from normalized data.
packages/frontend/.../segments.model.ts	Allows context-defined list types in forms.
packages/frontend/.../segment-list.helper.ts	Builds edit data and detects missing members.
packages/frontend/.../segment-list.helper.spec.ts	Covers normalization and edit-data behavior.
packages/backend/test/unit/services/SegmentService.test.ts	Tests persistence normalization.
packages/backend/test/unit/services/FeatureFlagService.test.ts	Tests feature-flag list normalization.
packages/backend/test/unit/services/ExperimentService.test.ts	Tests canonical legacy inference.
packages/backend/test/unit/controllers/validators/FeatureFlagListValidator.test.ts	Tests list-type validation.
packages/backend/src/api/services/SegmentService.ts	Normalizes segment list types before saving.
packages/backend/src/api/services/FeatureFlagService.ts	Normalizes feature-flag list writes.
packages/backend/src/api/services/ExperimentService.ts	Canonicalizes inferred experiment list types.
packages/backend/src/api/controllers/validators/FeatureFlagListValidator.ts	Requires string list types.
packages/backend/src/api/controllers/validators/FeatureFlagImportValidator.ts	Validates imported list types as strings.

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