Fix calculateTotal JavaScript example in documentation guidelines

[savvar9991]

What I Did

Updated docs/tone-voice.md code example:

• Added calculateTotal validation: Array.isArray + every for number/!NaN/isFinite (throws explicit errors).
• Removed unused apiKey const.
• Kept try-catch and output (60 on [10, 20, 30]).

+11 lines; full runnable JS.

Why Correct

• Matches standards: Complete examples, error handling, no placeholders.
• Fixes silent NaN/Inf (e.g., [10, NaN, 30] → Error, not NaN).
• Runtime-tested (Node.js equiv.)
  No breaks; boosts doc reliability.

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1