docs: roadmap index + custom-14a-command plans + backfill plan docs

- Add docs/plans/README.md as the roadmap index cataloguing all design/plan docs.
- Add the custom ISO14443-A command handling design + plan (L3 NTAG I2C
  SECTOR_SELECT / cross-sector reads + native auth; L4 static APDUs + WTX relay),
  produced from a multi-agent design workflow.
- Backfill previously-uncommitted plan docs (trace-formatter, ndef-trace-decode,
  live-sniff, firmware-upstream-rebase, 14a-live-trace) and NTAG5_SECURITY.md.
- Sync CLAUDE.md package structure with the committed transponder models.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CLAUDE.md

@@ -55,7 +55,17 @@ pm3py/
     access_control/        # Wiegand, OSDP
   transponders/            # tag/transponder models (extracted from sim/)
     hf/iso14443a/          # Tag14443A_3/4, MifareClassic, DESFire, NfcType2/4
+                           #   nxp/type2,ntag21x,ultralight,ntag_i2c
+                           #   (NTAG210-216, Ultralight/C/EV1, NTAG I2C plus)
+                           #   st/st25tn (Type 2), st/st25ta (Type 4)
+                           #   infineon/optiga_nbt (OPTIGA Authenticate NBT, Type 4)
+    hf/iso14443b/          # base.py: Tag14443B (SRIX slot-marker) +
+                           #   Tag14443B_4 (standard REQB/ATTRIB + ISO-DEP).
+                           #   Vendor models (organised by mfg, like the rest):
+                           #   st/st25tb, ti/rf430cl330h (NFC Type 4B)
     hf/iso15693/           # Tag15693, NfcType5, NXP ICODE/SLIX2/DNA/NTAG5
+                           #   st/st25tv, st/st25dv, infineon/myd_vicinity
+                           #   ti/tagit (Tag-it HF-I), ti/rf430frl (sensor)
     lf/                    # EM4100, HID, T5577
   reader/                  # higher-level reader modes by protocol/vendor (scaffold)
 ```