E2E test playbook `docs/testing/PI5_E2E.md`: staged, copy-paste checklists for testing on the real Pi 5 (rig smoke → serial kernel → first pixel → audio → playback → soak → OTA) + docs realignment of the Pi 5 pages

Epic: #113 · Milestone: MC9 — Ship

Why

The four Pi 5 docs (INSTALL_RPI5.md, RASPBERRY_PI_5.md, PI5_HARDWARE_MATRIX.md, QUICK_START_RPI5.md) describe target behaviour under a banner. The playbook is the measured procedure: every stage names the command, the expected serial/capture output, the pass criterion, and the issue that unblocks it. The initial content is the step-by-step in the epic #113; this issue keeps it current as gates land.

Tasks

• Stage 0 — Host setup (macOS): brew install zig qemu, build the Home compiler (cd ~/Code/Home/lang && zig build -Doptimize=ReleaseSafe, version pinned in scripts/zig-version.txt), export HOME_REPO=~/Code/Home/lang, Debug Probe serial (screen /dev/tty.usbmodem* 115200), enable macOS tftpd, capture dongle check.
• Stage 1 — Rig smoke: assembly UART banner (build.sh rpi5 --profile=smoke) → SD or TFTP → power → banner on serial.
• Stage 2 — Home kernel on serial: --profile=serial → milestones → shell commands → boot-pi5-serial script.
• Stage 3 — Storage/network: sd round-trip, lspci, usb, dhcp, ping.
• Stage 4 — Display/audio: fb-pi5-first-pixel, HVS test pattern, tone → capture FFT.
• Stage 5 — Media: reference clips from USB and NAS, gates, soak.
• Stage 6 — Product: flash the image, onboarding, CEC, phone remote, OTA round-trip, recovery.
• Troubleshooting table: no bootloader output (EEPROM/uart_2ndstage), rainbow/blank screen, image not loaded (kernel= name, DTB missing), EL mismatch, no network (link LEDs, PHY), HDMI no signal (EDID, mode), audio silent (N/CTS), capture dongle quirks.
• Realign the four docs: shrink to pointers at the playbook and status page; keep the ASPIRATION banner where measurement is missing.

Acceptance

A new contributor with the BOM reproduces Stage 1–2 from the doc alone; each later stage is updated in the PR that turns its gate green.

Size: S · Depends on: #48 · Blocks: —