feat: phases B and C (type ratchet, bridge tests, a11y, generator, OnPush)

[ghoshArnab]

Summary

Phases B and C of the modernization plan, stacked on #608 (base is chore/phase-a-modernization; retarget to master after #608 merges). See docs/adr/0002-phase-b-c-outcomes.md.

Phase B (additive)

• noImplicitAny per-file ratchet (npm run check:any); _bridge is clean.
• FieldBase<TValue = any> generic (non-breaking) + markForCheck() hook called by the bridge.
• Characterization tests for AngularPConnectService and the component map.
• axe-core accessibility checks for 12 field components.
• npm run new:component generator (scaffold + public-api.ts + component-map registration).
• npm run check:overrides type-checks the generated overrides package. This found a real bug: build-overrides left import type relative paths unrewritten, so the shipped field.base.ts in @pega/angular-sdk-overrides could not resolve its import. Fixed.
• Generated docs/components.md, plus testing and theming guides.

Phase C (where verifiable without Infinity)

• OnPush for 17 synchronous field components and 6 presentational components.
• Deferred with reasons in ADR 0002: signal inputs, OnPush for remaining components, secondary entry points, @defer, bridge split.

Needs review before merge

OnPush changes are unit-tested but not exercised end-to-end (Playwright needs a Pega Infinity server). Please run MediaCo portal + embedded before merging.

Checklist

• Conventional commits
• New components n/a (generator only; no new SDK components)
• Public API report refreshed (etc/angular-sdk-components.api.md)
• Tests added

Validation

• npm run lint — passed
• npm run build-angular-sdk-components — passed
• npm run test:unit — 131 passed, 43 skipped (legacy specs)
• npm run check:any, api:check, check:overrides, docs:components:check, smoke:pack — passed
• npm run build (test app) — passed
• Playwright E2E — not run