feat(jaeger): add new frontend system support

[RonitGandhi]

Closes #7538

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Adds new frontend system (alpha) support to the Jaeger plugin: registers the Jaeger API and the Traces entity content extension via a new ./alpha export. Legacy exports are unchanged. Closes #7538.

✔️ Checklist

• A changeset describing the change and affected packages. (more info)
• Added or updated documentation
• Tests for new functionality and regression tests for bug fixes
• Screenshots attached (for UI changes)
• All your commits have a Signed-off-by line in the message. (more info)

[backstage-goalie]

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
@backstage-community/plugin-jaeger	workspaces/jaeger/plugins/jaeger	minor	v0.18.0

[Copilot]

Pull request overview

Adds New Frontend System (alpha) support for the Jaeger workspace plugin, enabling installation via the @backstage-community/plugin-jaeger/alpha export and registering the plugin’s API + entity content extension for feature discovery / configuration.

Changes:

• Introduces src/alpha/* entrypoint with createFrontendPlugin, API blueprint, and entity content blueprint.
• Updates package exports and dependencies to include @backstage/frontend-plugin-api and @backstage/core-compat-api.
• Adds documentation and an API extractor alpha report, plus a changeset for the new capability.

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
workspaces/jaeger/yarn.lock	Locks newly added Backstage frontend-system dependencies.
workspaces/jaeger/plugins/jaeger/src/alpha/plugin.ts	Defines the alpha frontend-system plugin and binds legacy route refs.
workspaces/jaeger/plugins/jaeger/src/alpha/plugin.test.ts	Adds a basic unit test for the alpha plugin export.
workspaces/jaeger/plugins/jaeger/src/alpha/index.ts	Exposes the alpha plugin as the default export for /alpha.
workspaces/jaeger/plugins/jaeger/src/alpha/entityContents.tsx	Adds the entity content (tab) extension using compat wrapper + route ref conversion.
workspaces/jaeger/plugins/jaeger/src/alpha/apis.ts	Adds the API extension wiring jaegerApiRef to JaegerClient.
workspaces/jaeger/plugins/jaeger/report-alpha.api.md	Adds generated alpha API report reflecting the new exports/extensions.
workspaces/jaeger/plugins/jaeger/README.md	Documents how to install/configure the plugin in the new frontend system.
workspaces/jaeger/plugins/jaeger/package.json	Adds ./alpha export + typesVersions and required dependencies.
workspaces/jaeger/.changeset/jaeger-new-frontend-system.md	Declares a minor release for the new alpha frontend-system support.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 10 changed files in this pull request and generated 2 comments.

[RonitGandhi]

Thanks for the reviews! Rebased onto latest main (the branch had drifted and was conflicting) and pushed updates addressing everything:

@04kash — ran the changes against the plugin-new-frontend-system-support skill. The one migration step it flagged was the compat layer: the skill states that convertLegacyRouteRef/convertLegacyRouteRefs and compatWrapper are no longer required for plugin migration, and this workspace is on Backstage 1.52. So @backstage/core-compat-api is now dropped entirely — the existing @backstage/core-plugin-api route ref is passed directly to both createFrontendPlugin and EntityContentBlueprint, and the loader returns the component without a wrapper.

Walking the rest of the skill's checklist: this plugin contributes an entity content tab rather than a top-level page, so the PageBlueprint/SubPageBlueprint and dual-header steps don't apply — there's no page shell to split, JaegerComponent already renders Content only. The API is on ApiBlueprint, there are no translations or external route refs, and refs stay exported from the main entry point rather than being duplicated in ./alpha.

Copilot comments:

• Route key — agreed, switched entityContent → root to match the legacy plugin's route contract, and regenerated report-alpha.api.md.
• Test — rewritten. It now imports the default export through the public ./alpha entry point, asserts the API and entity content extensions are registered, pins the root route mapping, renders the Traces content against a mocked Jaeger API, and covers the annotation filter. Added @backstage/frontend-test-utils as a devDependency for this.
• README heading — Extensions config is now a level-3 subsection under New Frontend System.

yarn tsc, lint:all, test:all, and prettier:check all pass locally; API and knip reports regenerated.