Summary

Fixes #13781 — finally blocks (and if condition lines) were incorrectly marked as uncovered when all branches in try/catch had return statements.

Root cause

The coverage line count algorithm has two phases:

1. Phase 1: Find the innermost V8 range that fully encloses each line → use its count
2. Phase 2: Reset count to 0 if any zero-count range merely overlaps the line (even partially)

For try/catch/finally with returns, V8 emits a tiny zero-count range (often just 1 character) representing the unreachable sequential path between catch's return and the finally keyword. Phase 2's partial-overlap check let this tiny range incorrectly zero out the finally { line — even though Phase 1 correctly found a larger enclosing range with count > 0.

The same bug affected if (cond) { lines where the false-branch zero-count range partially overlapped the condition line.

Fix

Phase 2 now uses the same full-enclosure criterion as Phase 1, and only overrides when the zero-count range is more specific (smaller) than the best range found in Phase 1.

Test plan

• Reproduction from deno coverage doesn't mark finally if try/catch have return statements #13781 now reports 100% line coverage
• All 16 existing coverage spec tests pass (2 had expectations updated to reflect correct behavior)

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