feat(skills): IoT firmware leaf playbooks (acquisition, binwalk-extract, hardcoded-creds, U-Boot, dev-mem)

[VoidChecksum]

Summary

Creates five leaf playbooks that were referenced in standard/iot/SKILL.md but did not exist, resolving all dangling catalog links in the IoT subdomain.

Leaves added

Slug	Path	Covers
firmware-acquisition	standard/iot/firmware-acquisition/SKILL.md	Vendor portals, OTA MITM proxy capture, SPI NOR dump (flashrom/CH341A + SOIC-8 clip), eMMC chip-off + dd, UART/JTAG console dumps with U-Boot tftp exfil
binwalk-extract	standard/iot/binwalk-extract/SKILL.md	binwalk recursive extraction, entropy analysis, squashfs (standard + sasquatch vendor variants), JFFS2 (jefferson + mtdram mount), UBIFS (ubireader), manual byte-pattern carving, firmware-mod-kit nested containers
hardcoded-creds	standard/iot/hardcoded-creds/SKILL.md	/etc/shadow + passwd parsing + hashcat/john cracking, busybox httpd + Dropbear key extraction, strings sweep + trufflehog FS scan, MQTT/cloud API token extraction, default-credential matrix, TLS private key harvesting
bootloader-uboot	standard/iot/bootloader-uboot/SKILL.md	Autoboot interrupt (manual + UART break), printenv/setenv, bootargs init=/bin/sh override, persistent saveenv modifications, secure-boot bypass (FDT patch, HAB status, rollback), fault injection with ChipWhisperer-Nano and crowbar glitch
dev-mem	standard/iot/dev-mem/SKILL.md	/dev/mem reads/writes (devmem2, dd), STRICT_DEVMEM bypass paths, MTD partition dump + erase + flashcp write, U-Boot env CRC-patching via MTD, /proc/kallsyms symbol resolution, live process memory access via /proc/pid/mem

Notes

• Additive markdown only — no existing files modified.
• standard/iot/SKILL.md routing table unchanged; these files fulfill its existing references.
• All five SKILL.md files follow the frontmatter schema (name, description, allowed-tools, metadata.{subdomain,when_to_use,tags,mitre_attack}) copied from standard/wireless/wpa2-psk/SKILL.md.
• ruff check/format and skills-registry pytest suite pass clean on this branch.