fix: ensure enclosing ranges contain occurrences

[mskry]

Test plan

Reproduction

Use the existing enclosing-range fixture:

const test = () => {
  return 'value'
}

Before the fix, the occurrence covered test, while the enclosing range covered only the initializer:

occurrence:       test
enclosing range:         () => { ... }

The source-file occurrence had the same problem when the file started with comments: its occurrence was at [0,0,0], but its enclosing range started after the leading comments.

The new snapshot assertion fails when either malformed range is generated.

Verification

• Added an assertion that every emitted enclosing_range contains its occurrence.
• Updated the source-file and function-valued-variable snapshots.
• Ran npm run test: 31/31 passed.
• Ran npm run build.
• Ran npm run prettier-check.
• Ran npm run eslint.