Adds docs/imac19-2-speaker-fix.md: internal speakers produce no sound
despite correct HDA-level plumbing (unmuted volume, enabled pin, clean
device open). Traces the likely cause to uninitialized external TAS5764L
amp chips and a CS42L83 companion codec behind the CS8409, via sibling-
model prior art (rojoxstar/imac19-2-cs8409-linux, egorenar/snd-hda-codec-
cs8409#31, network-garden-lab's Fedora-specific iMac18,3 patch). No fix
is packaged yet given the amp-register damage risk and the bigger lift
of patching in-tree kernel source rather than an out-of-tree module.
Also adds docs/chromium-dbus-singleton-activation.md and a new "Software
fork directions" README section indexing forward-looking fork/patch
write-ups separately from the hardware-specific patches already shipped.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
