fix(observable): add explicit extensions to relative ESM imports

[odinr]

Why is this change needed?
@equinor/fusion-observable's relative import/export specifiers (e.g. ./operators, ../types) had no file extensions. The package's tsconfig inherits moduleResolution: "bundler" from the repo root, so tsc never rewrote these to .js//index.js in the compiled ESM output. That's fine for bundler-based consumers (Vite/webpack), but breaks strict Node.js ESM resolution for any consumer that resolves the published dist/esm output directly (e.g. Vitest running without a bundler), producing module-not-found errors. A downstream consumer had already worked around this with a yarn patch.

What is the current behavior?
Compiled dist/esm/*.js files import sibling modules without extensions (from './operators'), which fails to resolve under strict Node ESM.

What is the new behavior?
Every relative import/export in src/**/*.ts now has an explicit .js (file) or /index.js (directory) extension, so the compiled output resolves correctly under both bundler and strict Node ESM resolution. The package's own tsconfig.json now overrides module/moduleResolution to nodenext so tsc enforces explicit extensions going forward instead of silently allowing them to be omitted again.

What is the intended behavior or invariant?
@equinor/fusion-observable's published ESM output must be resolvable by both bundler-based and non-bundler (native Node ESM) consumers. The package-local nodenext override only affects how this package type-checks its own imports; it does not change how other packages (still on moduleResolution: "bundler") consume this package's emitted .d.ts/.js output.

Does this PR introduce a breaking change?
No. Output paths and public API are unchanged; only the internal module specifiers gained explicit extensions.

Impact assessment:

• Breaking changes: No
• Version bump: Patch (changeset included)
• Consumer impact: Fixes resolution for consumers that load the package's ESM output directly (without a bundler), e.g. Vitest/Node-based tooling.
• Downstream impact: Verified other in-repo consumers (e.g. packages/react/app, packages/modules/*, packages/dev-portal) still build cleanly via tsc -b since they still use moduleResolution: "bundler" and consume the emitted declaration/JS files, not the source.

Review guidance:
Diff is mechanical (adding extensions) across ~30 files in packages/utils/observable/src; the interesting parts are tsconfig.json (the nodenext override) and FlowSubject.ts as a representative example. Verified: tsc -b --force, vitest run (42/42 tests), biome check, and fusion-lint all pass; a downstream project-reference build (packages/react/app) also builds clean.

Additional context
The two dead test files under src/__tests__/ (Query.test.ts, ReactiveObservable.test.ts) reference modules that no longer exist and are excluded from both this package's tsconfig.json and its vitest.config.ts (test.include: ['tests/**']); they were intentionally left untouched as out of scope.

Related issues
None.

Checklist

• Confirm completion of the self-review checklist
• Confirm TSDoc captures intent for functions, hooks, components, classes, and named arrow functions (no TSDoc content changed)
• Confirm iterator blocks, decision gates, RxJS chains, and complex decisions explain why they exist (unchanged)
• Confirm React logic and derived values are resolved before markup when applicable (n/a)
• Confirm README/docs are updated for user-facing changes (n/a, internal fix)
• Confirm changes to target branch validation
  • Included files validated
  • No new linting warnings
  • Not a duplicate PR
• Confirm adherence to code of conduct

[changeset-bot]

🦋 Changeset detected

Latest commit: bd1fbb7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 15 packages

Name	Type
@equinor/fusion-observable	Patch
@equinor/fusion-framework-dev-portal	Patch
@equinor/fusion-framework-module-analytics	Patch
@equinor/fusion-framework-module-telemetry	Patch
@equinor/fusion-framework-module-widget	Patch
@equinor/fusion-framework-react-app	Patch
portal-analytics	Patch
@equinor/fusion-framework-cli	Patch
@equinor/fusion-framework-app	Patch
@equinor/fusion-framework	Patch
@equinor/fusion-framework-vite-plugin-spa	Patch
@equinor/fusion-framework-vitest-plugin-react-app	Patch
poc-portal	Patch
portal	Patch
@equinor/fusion-framework-dev-server	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR

[Copilot]

Pull request overview

Fixes strict Node.js ESM resolution for @equinor/fusion-observable.

Changes:

• Adds explicit .js or /index.js extensions to relative module specifiers.
• Enables NodeNext resolution to enforce valid ESM imports.
• Adds a patch changeset.

Reviewed changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
.changeset/observable_fix-esm-import-extensions.md	Documents the ESM resolution fix.
packages/utils/observable/tsconfig.json	Enables NodeNext module resolution.
packages/utils/observable/src/types/reducers.ts	Adds an explicit import extension.
packages/utils/observable/src/types/index.ts	Adds explicit export extensions.
packages/utils/observable/src/to-observable.ts	Adds an explicit import extension.
packages/utils/observable/src/react/useObservableState.ts	Uses the explicit types entry point.
packages/utils/observable/src/react/useObservableSelectorState.ts	Adds explicit relative extensions.
packages/utils/observable/src/react/useObservableSelector.ts	Adds explicit relative extensions.
packages/utils/observable/src/react/useObservableRef.ts	Adds explicit relative extensions.
packages/utils/observable/src/react/useObservableInputState.ts	Adds explicit hook import extensions.
packages/utils/observable/src/react/useObservableFlow.ts	Adds explicit type import extensions.
packages/utils/observable/src/react/useObservableEffect.ts	Adds explicit type import extensions.
packages/utils/observable/src/react/useObservable.ts	Adds explicit relative extensions.
packages/utils/observable/src/react/useDebounce.ts	Uses the explicit types entry point.
packages/utils/observable/src/react/use-observable-epic.ts	Adds an explicit hook import extension.
packages/utils/observable/src/react/index.ts	Adds explicit React barrel extensions.
packages/utils/observable/src/operators/switch-map-action.ts	Adds explicit operator import extensions.
packages/utils/observable/src/operators/map-prop.ts	Uses the explicit types entry point.
packages/utils/observable/src/operators/map-action.ts	Adds explicit operator import extensions.
packages/utils/observable/src/operators/index.ts	Adds explicit operator barrel extensions.
packages/utils/observable/src/operators/filter-action.ts	Uses the explicit types entry point.
packages/utils/observable/src/index.ts	Adds explicit root barrel extensions.
packages/utils/observable/src/FlowSubject.ts	Adds explicit internal module extensions.
packages/utils/observable/src/create-state.ts	Adds explicit internal module extensions.
packages/utils/observable/src/create-reducer.ts	Adds explicit type import extensions.
packages/utils/observable/src/actions/utils.ts	Adds an explicit action import extension.
packages/utils/observable/src/actions/predicates.ts	Adds explicit action import extensions.
packages/utils/observable/src/actions/index.ts	Adds explicit action barrel extensions.
packages/utils/observable/src/actions/create-async-action.ts	Adds explicit action import extensions.
packages/utils/observable/src/actions/create-action.ts	Adds explicit import and export extensions.
packages/utils/observable/src/actions/ActionError.ts	Adds an explicit type import extension.
packages/utils/observable/src/actions/action-mapper.ts	Adds an explicit type import extension.

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