ReadNfcTagTool
Reads NDEF data from the most recently scanned NFC tag.
Does not actively scan: it returns the tag cached in NfcTagCache, which the host Activity populates from onNewIntent() via NFC foreground dispatch. Requires NFC to be available and enabled. Read-only.
Output keys: has_tag; when a tag is cached, tag_id (hex), is_ndef, and tech_list (non-NDEF tags) or is_ndef/max_size/is_writable/records (each record: tnf, type, payload). When no tag is cached: has_tag false plus a message.