analytics: report sessionDepth as a number in both analytics generations - #385

Why

sessionDepth reached consumers as a string or a number depending on timing: sessionStorage stringifies on write, so a stored depth read back as "3", while the || 1 fallback supplied the number 1 when the key was missing. The parity harness caught the two types on one field.

What changed

• optable.prebid.auction payloads report sessionDepth as a number in every case, where a session with a stored depth previously sent a string.
• auction_processed payloads do the same, reading optableSessionDepthIndex through Number().
• No case changes value: the writers start at 1, so the "0" the old truthiness check would have passed through never occurs.

How to Test

• Tested
• Docs updated — if this adds, changes or removes anything a consumer calls, update the module's .md alongside the code (for example lib/addons/<addon>.md) and the matching README section. New addons ship with a new .md.

Notes

• Breaking change
• Requires release