feat: form actions can be written in typescript

[romain-pm]

Summary

Form actions can now be written in TypeScript. The three built-in email/forward actions are converted to TS implementations in formidable-elements; save-to-JCR stays in Java. Existing forms and action configurations keep working unchanged.

Why

Formidable's action SPI was Java/OSGi-only, while the rest of the module family is moving to JavaScript modules. With the JSServerExtensionInvoker SDK landing in javascript-modules-engine 1.3.0, consumer modules can define their own JS extension types — this PR uses it so site developers (and Formidable itself) can author actions in TypeScript without a Java bundle.

Changes

• JS dispatch bridge: new JsFormActionDispatcher consuming the formidable-form-action registry type (keyed by node type); FormSubmissionPipeline falls back to it when no Java FormAction matches. Java handlers win on conflict; no handler at all still yields FMDB-008 with progress counters.
• Graceful degradation: the SDK reference is optional end-to-end (optional DS reference + resolution:=optional manifest import) — on a pre-1.3.0 engine, formidable deploys and Java actions keep working.
• Security stays in Java: new exported FormActionSupport service (SSRF-checked forwardSubmission — target URL never exposed to JS —, capped buildEmailAttachments, upload-size accessor).
• TS actions + wrapper: registerFormAction wrapper ({ok, status, message} wire contract, Java FormActionException statuses preserved) and TS ports of emailNotification, emailContent, forward in formidable-elements/src/server/; TemplateInterpolator/FieldEscaper logic ported with vitest coverage.
• CND ownership: the 3 action node types (+icons, +en/fr labels) move to formidable-elements, next to their handlers (see updated docs/cnd-module-ownership.md); fmdbmix:formAction and fmdb:save2jcrAction stay in the engine.
• Samples & tests: raw-contract TS sample actions in formidable-test-module-samples-tsx, new Cypress spec (tests/cypress/e2e/actions/70-ts-form-actions.cy.ts), Mailpit added to the e2e docker-compose, new/retargeted engine unit tests.

Validation

• mvn clean install green across all 8 modules (engine: 155 unit tests; elements: tsc + eslint + 14 vitest)
• Server bundles verified to contain the registered actions; engine manifest carries the optional sdk;version="[1.3,2)" import
• Cypress e2e (needs the docker environment with the SDK-enabled engine)
• Manual verification on a local Jahia (emails via Mailpit, forward via echo endpoint, both locales)

Documentation

• docs/how-to-create-form-action.md: new TypeScript section (wrapper usage, raw registry contract, FormActionSupport)
• docs/cnd-module-ownership.md: action-type ownership rule updated

Dependency / draft status

⚠️ Depends on javascript-modules feature/js-server-extensions-sdk (exports org.jahia.modules.javascript.modules.engine.sdk from javascript-modules-engine:1.3.0-SNAPSHOT). CI cannot compile formidable-engine until that branch is merged and a snapshot is published — keeping this PR draft until then. Once 1.3.0 is released, also consider pinning <jahia-depends>javascript-modules-engine=1.3.0</jahia-depends>.

[github-actions]

🦜 Chachalog

formidable minor

• Added support for writing custom form actions in TypeScript, alongside Java. The built-in
  email and data-forwarding actions are now TypeScript implementations; forms and existing
  action configurations keep working unchanged.

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[github-actions]

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