docs(dankclaw): record the 64 GiB host swapfile and its safe resize ordering

Raised /swap.img from 8 GiB to 64 GiB on Dankclaw. Host-level state with no
repo file, so it was invisible to the repo until now: fstab line 12 drives the
generated swap.img.swap unit, ext4, fallocated hole-free, swappiness 60,
zswap off. 748 GiB still free on /.

The reusable part is the ordering. The old file held 4 GiB of live pages and
MemAvailable read 73 GiB while only ~5 GiB was genuinely free -- the pinned
model weights are counted as reclaimable page cache, so the headline lies by
the size of the model. Swapping off before the replacement is online would have
pushed those pages into RAM that does not exist. Creating and enabling the new
swap first let them migrate instead: swapoff took 65 s and the host never
wobbled.

New page serverAppConfigs-docs/Dankclaw/Swap Configuration.md, linked from
the index, plus a pointer in the AGENTS.md memory-model section so nobody
reasons about headroom without checking swapon.

Old 8 GiB file staged at dankclaw:~/.AGENTTRASH/20260912-swapfile-8g/
pending approval to purge.

serverAppConfigs-docs/index.md

@@ -144,6 +144,10 @@ The LLM inference fleet on the two hosts. Full index:
 - [[Dankserver System Specs]] — the RTX 3090 box hardware
 - [[Dankclaw System Specs]] — the Strix Halo gfx1151 box (frank-large)
 - [[Dankclaw Improvements]] — host-level changes on the Strix Halo box
+- [[Swap Configuration]] — the 64 GiB `/swap.img` host swapfile (raised from
+  8 GiB 2026-09-12): fstab-driven `swap.img.swap` unit, the safe resize
+  ordering that drains the old file into fresh swap instead of into a host
+  whose `MemAvailable` lies by the size of the model, and the swappiness caveat
 - [[frank-npu]] — the RETIRED FLM NPU endpoint on Dankclaw (2026-09-11):
   Gemma4 E4B vision+audio pack on the XDNA2 NPU, port 7771; kept as the
   retirement record, including the IOMMU/SVA err=-19 root cause and