Gmail collection dev guide; correct the two now-false claims New: Gmail-Mail-Collection-Developer-Guide - the labels-not-folders model, the labelIds=INBOX bug and why an empty result set hid it, and the resultSizeEstimate trap with the measured numbers. Corrected in the existing pages, because #1173 made them untrue: - Verification guide s6 documented labelIds=INBOX as a known limitation deliberately not fixed. It is fixed, so the section is rewritten and the amber note it described is inverted. - Issue-45-Verify write-up claimed "201 messages - real account data". That number came from resultSizeEstimate and was fiction; INBOX actually holds 2.