Experiments Portlet — migration: delete the old per-page experiments UI and remove the flag

Description

The epic's strategy is: build the new portlet complete, then migrate and delete the old one. This is the issue where the duplication ends. It is filed up front — together with the rest of the epic — so "delete old later" is a scheduled step, not a wish that never happens.

This is deliberately the only issue that rewrites/removes existing code at scale.

Entry condition: every "port" row of the functional-parity inventory verified working in the new portlet on the dev/QA instance, and the E2E suite (#37006) green. Nothing is deleted before its replacement is verified.

Delete

• The old per-page UI in libs/portlets/dot-experiments/portlet/src/lib/: dot-experiments-shell/, dot-experiments-list/ (including the drawer create component), dot-experiments-configuration/, dot-experiments-reports/, dot-experiments-analytic-app-misconfiguration/, the old shared/ tree, and the old lib.routes.ts (dotExperimentsRoutes).
• With them go: the three @ngrx/component-store stores, the 10 hardcoded router.navigate(['/edit-page/…']) calls, and the window.location.href-parsing getUrl() — no decoupling refactor needed; the code that holds them disappears.

Rewire

• UVE entry point permanently targets the new flow; remove FEATURE_FLAG_EXPERIMENTS_PORTLET — the entry-point flag introduced by #37005 — its withFlags wiring, its FeaturedFlags entry, its ConfigurationResource allow-list entry, and its explicit false in dotmarketing-config.properties.
• Do not remove FEATURE_FLAG_EXPERIMENTS. Despite the name, it is not a frontend flag: it is the backend kill-switch for the whole Experiments feature, read by ConfigExperimentUtil.isExperimentEnabled() and gating experiment JS injection (ExperimentWebAPIImpl:338) and experiment resolution during page render (HTMLPageAssetRenderedAPIImpl:176,239). Removing it would stop experiments from serving to visitors. It keeps its name, meaning, default and consumers. The unused enum entry FeaturedFlags.LOAD_FRONTEND_EXPERIMENTS = 'FEATURE_FLAG_EXPERIMENTS' (shared-models.ts:28) never gained a consumer and can be deleted here — the property cannot.
• Update libs/portlets/edit-ema/portlet/src/lib/lib.routes.ts:117 (the lazy import of dotExperimentsRoutes) and the nav spec dot-ema-shell.component.spec.ts:117-120 to the new routes.
• Promote site-wide/ to the lib root; the components copied into site-wide/shared/ become the only copies.

Clean up

• Move the chart colors in libs/dotcms-models/src/lib/dot-experiments.model.ts:204-215 behind a lazy getter, removing the import-time getComputedStyle(document.body) and the spec stubs #36989 added.
• Remove i18n keys used only by the deleted screens.
• Remove AllowedActionsByExperimentStatus keys that no longer have a consumer (verify — the matrix itself stays; the new portlet reads it).

Acceptance Criteria

• Entry condition documented as met: parity checklist signed off on dev/QA; #37006 green.
• The old tree and dotExperimentsRoutes are gone; pnpm nx build dotcms-ui and all specs pass.
• UVE experiments entry lands in the new flow with no flag involved; FEATURE_FLAG_EXPERIMENTS_PORTLET and its consumers are removed.
• FEATURE_FLAG_EXPERIMENTS and its backend consumers are untouched; experiments still serve to site visitors after the migration.
• No import of @ngrx/component-store remains under libs/portlets/dot-experiments/.
• dot-experiments.model.ts no longer runs getComputedStyle at import time.
• The whole E2E suite passes (the FEATURE_FLAG_EXPERIMENTS_PORTLET-off regression spec is retired with that flag).
• Grep proof in the PR: no edit-page/… navigation remains under the experiments lib.

Priority

Low until Screens 1-3 + UVE land; then it is the closing step of the epic.

Additional Context

• Depends on: #36989, #37003, #37004, #37005, #37006, #37007.
• Out of scope: registering the portlet for customers (UpgradeTask + starter bump) — separate decision, gated on #36823's permission filtering being in the build.
• Verify: pnpm nx lint|test portlets-dot-experiments-portlet · pnpm nx test portlets-edit-ema-portlet · pnpm nx test dotcms-ui --testPathPattern=app.routes · pnpm nx build dotcms-ui · npx playwright test --grep @experiments

First verify the parity checklist and #37006, then inspect the old tree under libs/portlets/dot-experiments/ and the routes in edit-ema/lib.routes.ts:117. Run the listed portlet, dotcms-ui, build, and Playwright checks while removing the old routes and flag wiring. Done means the old tree and flag are gone, backend FEATURE_FLAG_EXPERIMENTS consumers remain untouched, and all checks pass.