refactor: resolve naming collision and edge cases in coverage attribution engine

[yvonnedevlinrh]

Context

Follow-up from review of #226 (per-requirement test attribution). All findings are non-blocking and were deferred to keep the PR focused per Constitution Principle III.

Findings

1. EnrichWithTestResults / enrichWithTestResults naming collision (MEDIUM)

internal/coverage/coverage.go now contains two functions with near-identical names but completely different signatures and semantics:

Function	Line	Visibility	Signature	Behavior
enrichWithTestResults	284	unexported	(ctx, report, opts) error	Runs tests, mutates report entries (gap-reporting engine)
EnrichWithTestResults	522	exported	(mapping, results) map[...]	Pure function, returns new requirement→status map (attribution engine)

A reader will assume the exported version is a promoted refactor of the unexported one. In reality they serve different subsystems.

Suggested fix: Rename the exported function to ClassifyRequirementTestStatus or MapRequirementsToTestStatus to distinguish it from the gap-reporting function.

2. Regex [\da-z]+ admits _test as a valid sub-segment (LOW)

The requirementPattern regex at coverage.go:416:

^(a-z+)(\d+(?:\da-z+)*)$

After TrimSuffix(segment, "_test"), a pathological package name like data.policy.ac_2_1_test_test becomes ac_2_1_test, which the regex matches as ac-2.1.test. No real requirement ID uses .test as a sub-segment, so this is theoretical.

Suggested fix: Either restrict the character class (e.g., require digits-first in sub-segments) or add a post-match filter rejecting sub-segments that equal "test".

3. Details nil vs empty-slice inconsistency (NIT)

In internal/tester/runner.go:

• Empty files path (line 29): returns Details: []testresult.Detail{} (non-nil empty slice)
• All-skipped path (line 66): Details remains nil (zero value from &Results{})

Not a bug — all consumers use len() which handles both — but the inconsistency could surprise future callers checking == nil.

Suggested fix: Initialize Details to []testresult.Detail{} at line 66 as well.

Acceptance criteria

• Exported EnrichWithTestResults renamed to eliminate collision with unexported enrichWithTestResults
• All callers updated (coverage.go, coverage_test.go)
• Tests pass, lint clean