fix(auth): type-check test files via tsconfig IDE/build split

[nshirley]

Because:

• fxa-auth-server's tsconfig orphaned spec files (specs excluded, test/ never included), so editors showed spurious "Cannot find name 'describe'" and real spec type errors were silenced (FXA-13782).

This commit:

• tsconfig.json (IDE) includes test/ + moduleDetection:force so legacy require()-style specs get jest types without colliding.
• Adds tsconfig.build.json (excludes specs/test) for emit + CI type-check, keeping dist test-free and compile green; points build-ts/compile at it.

Closes: FXA-13782

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[Copilot]

Pull request overview

Adjusts fxa-auth-server’s TypeScript configuration to type-check test/spec files in editors (surfacing real test type errors and enabling Jest globals), while keeping build/CI emit and compile checks focused on shippable code only.

Changes:

• Update tsconfig.json (IDE default) to include test/**/* and force module detection to avoid global-scope collisions among legacy require()-style specs.
• Add tsconfig.build.json to exclude tests/specs for emit and CI --noEmit type-checks.
• Point build-ts and compile scripts at tsconfig.build.json.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
packages/fxa-auth-server/tsconfig.json	Includes test/**/* for IDE type-checking and sets moduleDetection: "force" to prevent spec-file global redeclare errors.
packages/fxa-auth-server/tsconfig.build.json	New build/CI config extending IDE config but excluding tests/specs and restoring prior module detection behavior.
packages/fxa-auth-server/package.json	Routes build/type-check scripts through tsconfig.build.json and aligns tsc-alias invocation accordingly.

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