Assert Hestia's headless invariant -- FABRIC-3.6.md task 1.9, Phase 1 closed

Audited first: neither capsules/hestia/init.4th nor her birth block in
kernel_main.c references g_wirebind_attached_username, CONSOLE-ATTACH,
MINT, or any proxy-minting mechanism -- the invariant already held
structurally, by absence. Stated it explicitly anyway, per the task:
added a comment at Hestia's birth site quoting FABRIC-3.5.md SXVIII.6's
invariant verbatim, warning future edits not to add console/wirebind/
proxy code there without re-reading it first.

Verified live with the actual no-thumbdrive boot
(ARCH=<arch> qemu ZUSEDISK=), not the default. All four VMs born
successfully on all three architectures, zero UNKNOWN WORD, and zero
ok> occurrences anywhere in any of the three full logs -- genuinely
silent, matching sk_repl_headless_wait()'s own documented "no banner,
no prompt, no input surface at all." Watched each log's line count
post-birth for 8-10s to confirm it stayed flat rather than eventually
printing something late.

Confirmed no regression on the standard (with-thumbdrive) path on
amd64: dict_hash identical to task 1.8's baseline. Did not repeat that
check on aarch64/riscv64 -- the change is a comment only, cannot
diverge by compiler, and the headless invariant itself was already
proven identically on all three.

Phase 1 is now fully closed (tasks 1.1-1.9). Tripod is Hera/Artemis/
Hestia plus Hermes (retained through Phase 1-3 per SXXXIV.4); Hestia
owns the drawing fabric exclusively; headless-until-login intact with
Hestia in the fleet. Phase 2 is next.

Authorized by Captain Bob ("yes").

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

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