DOCFIX-189: re-audit the max-context session's troubleshooting + docs ...

Operator-instructed re-evaluation. The 2026-07-12 session authored its docs and
module comments WHILE WORKING FROM A WRONG DIAGNOSIS, at a context limit, so its
reasoning was re-checked rather than just its one-line bug (DOCFIX-188).

Headline: the settings it changed are mostly fine and are RETAINED. The reasoning
it recorded was not -- it attributed the fault to whatever knob was being turned,
on no evidence, four separate times. It also left one silently-dead knob.

FALSE CAUSAL CLAIMS (corrected at the source, opnsense-edge/main.tf). The disk
shape, q35->i440fx, the serial console and svm-disable were EACH written up as a
contributing cause. None changed the symptom -- the fault sat at a deterministic
262 bytes through all of them. All four settings RETAINED (each defensible on its
own merits); only the false justifications are gone. The serial console earned its
keep, but it REVEALED the fault, it did not change it.

DEAD KNOB (real functional defect). `disk_size_bytes = 16 GiB` did nothing once
DOCFIX-187 made the disk a direct copy; unused variables are legal HCL so neither
validate nor plan complained. MEASURED: the live disk is 11.00 GiB, not 16.
Removed from main.tf + module variables; real sizing is opnsense-prep-image.sh's
GROW (+8G). Proof it was dead: tofu plan is byte-identical before/after removal.

STALE/UNSOURCED FACTS. "Opteron_G3" is a red herring -- the host is really an AMD
EPYC 9965 (Zen 5, family 26); libvirt's CPU-model DB doesn't know family 26 and
falls back to the oldest name, and the prior session partly built its nested-virt
theory on that artifact. "OPNsense's 3 GB min" is unsourced -- annotated, do not
propagate. DOCFIX-186's backing_store parenthetical is stale (same conclusion,
different mechanism). DOCFIX-187's changelog gains a SUPERSEDED-IN-PART header.

KEPT: DOCFIX-186's apparmor + config-iso-staging findings are real and measured.
DOCFIX-185 (operator transport ruling) untouched.

STANDING LESSON: when a change does not fix the symptom, do not write it up as
though it did. A fault that is deterministic and immune to every knob you turn
means you have not yet touched the cause.

Gauntlet ALL GREEN (52); repo-lint 0 fail; tofu fmt/validate/plan clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y117t1F525ba9r1vXSBETk