Enable in-container USB flashing + flash-re-bba-rb skill; find U7 EEPROM undersized

Devcontainer now grants libusb access to the FT2232H so iceprog (bitstream) and
pyftdi (FT2232H EEPROM) run inside the container:
- devcontainer.json: --privileged + /dev/bus/usb bind mount
- Dockerfile: sudo (NOPASSWD for vscode; USB nodes are root-owned), libusb-1.0-0,
  libftdi1-2, pyftdi

Add the flash-re-bba-rb skill documenting the procedure (bitstream via best swept
seed, optional EEPROM string, troubleshooting, guardrails) and
flash_ftdi_eeprom.py (pyftdi, backup-first, dry-run default) + ftdi_eeprom.conf
value spec.

Bring-up on the repaired V1 unit: bitstream flash VERIFY OK (iceprog
build/seed4/top.bin, capture 58.36 MHz). EEPROM product string CANNOT be
programmed on V1 — U7 is a 93LC46B (128 B), too small for the FT2232H, which
needs a 93LC56B (256 B); the 128 B chip mirrors and the config write fails
verify. This overturns the old REVIEW note "93LC46B = correct for FT2232H"
(that only checked ORG, not size). Board still works blank -> ROM defaults;
iceprog + UART unaffected. Documented in REVIEW.md + TODO.md (swap U7->93LC56B
for V2); flash_ftdi_eeprom.py detects the mirroring and refuses the write.

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

hardware/re-bba-rb/TODO.md

@@ -358,6 +358,15 @@ Major work this session:
 
 ## Minor / BOM
 
+- [ ] **U7 EEPROM undersized — swap 93LC46B → 93LC56B for V2 (found at bring-up
+      2026-08-22).** The 93LC46B is 128 B; the FT2232H needs ≥256 B (93LC56B /
+      93LC66B) to hold its config, so the "re-BBA-rb" USB product string can't be
+      programmed on V1 (write mirrors + fails verify — see REVIEW.md "U7 PART IS
+      UNDERSIZED"). **Not a functional blocker:** V1 ships with U7 blank → FT2232H
+      ROM defaults ("Dual RS232-HS", 0403:6010); iceprog bitstream flash (VERIFY
+      OK on the repaired unit) and the channel-B UART are unaffected. 93LC56B is
+      the same SOIC-8 / fixed-16-bit-org, pin-compatible drop-in. Pick a JLC part
+      (e.g. 93LC56BT-I/SN) when respinning.
 - [x] RSET_BG 12.4 k — ACCEPTED 2026-07-18 (closed, no change): datasheet
       says 12.3 kΩ, but that is an E192 value with no JLC Basic part —
       WIZnet's own reference synthesizes it as 12 k + 300 Ω. The 0.8 %