Add comprehensive tests in scorer_test.go: unsupported language → N/A, unmeasured complexity not scored as excellent, Swift-like generic unit produces no fabricated dimensions, and regression tests for each fix area. #26

Add comprehensive tests in scorer_test.go: unsupported language → N/A, unmeasured complexity not scored as excellent, Swift-like generic unit produces no fabricated dimensions, and regression tests for each fix area.

Split from parent issue:#21 by Tier-1 auto-split (#800).

Target files:

• internal/engine/scorer_test.go

Non-goals:

• Do NOT change production code in this step — only tests
• Do NOT modify language_tiers.go
• Do NOT touch report generation or init_cmd.go

Verification command: go test ./... -count=1
Size: m
Risk: medium

Add to internal/engine/scorer_test.go:

1. TestScore_UnsupportedLanguage_ReturnsNA — construct a unit whose language is 'Swift' (or any TierGeneric language). Call Score(). Assert Grade == "N/A". Assert Unsupported marker is true. Assert no dimension scores are present (or all are sentinel 'unmeasured').

2. TestScore_UnmeasuredComplexity_NotScored — construct a unit with complexity=0 from a TierGeneric language. Call scoreFromMetrics (or Score). Assert that the maintainability dimension is NOT scored as 0.95 (excellent). It should be absent or marked unmeasured.

3. TestScore_SupportedLanguage_StillWorks — construct a Go unit with real metrics. Call Score(). Assert it produces a real grade (A/B/C/D/F, not N/A) and has populated dimension scores. This is a regression guard.

4. TestScore_DefaultsNotInjected — construct a TierGeneric unit. Call Score(). Assert that no dimension has value 0.5 (the old default). All unmeasured dimensions should be absent from the dimension map.

5. TestScore_AggregateSkipsUnsupported — if scorer.go has aggregate logic, test that unsupported units are excluded.

Run go test ./... -count=1 and fix any failures.