TigerTag: read tag index and tag count

[TigerTag-Project]

TigerTag spec v2.2 adds a tag index / tag count byte (section 2.11), so a reader knows which tag it just read and how many tags the item carries. For example, a spool with one tag on each side is "tag 1 of 2" and "tag 2 of 2". This PR lets OpenRFID read it.

Format

Offset +39 (page 0x0D, byte 3). The high nibble is the tag index, the low nibble is the tag count:

• 0x00: unknown. Every tag written before v2.2 has this value, so existing tags keep working.
• 0x11: single tag
• 0x12 / 0x22: twin tag, tag 1 of 2 / tag 2 of 2

The byte is not covered by the TigerTag+ signature.

Changes

• GenericFilament: new tag_index and tag_count fields. They default to 0 (unknown), so other processors are unaffected. Both are included in to_dict(), so they reach the webhook. pretty_text() shows "Tag: 1 of 2" when the count is known.
• TigerTag parser: reads the byte. An index higher than the count is treated as unknown.
• Tests:
  • The official TigerTag+ dumps (eSun, R3D, Rosa3D, Sunlu) come from spools that carry twin tags, but were written before v2.2. They are updated to "tag 1 of 2" (0x12). Only byte +39 changes, and every signature still verifies against the TigerTag+ public key, since this byte is not signed.
  • A new eSun PLA Basic Refill Cold White TigerTag+ Twin 2 of 2 copy covers the second index (0x22). It gives the same unique_id as tag 1, as expected: twin tags share the same timestamp (section 2.9), so OpenRFID sees them as the same spool.
  • The Elegoo dump, a plain TigerTag written before v2.2, checks that such tags read as unknown (0/0).

97 passed, 1 skipped.

Note: #32 also adds fields at the end of GenericFilament and to_dict(). Whichever is merged second will need a trivial conflict resolution there; happy to rebase.