docs: storage plan — fix two id-path leftovers (DANOS/label->hex)

Two spots still said /volumes/DANOS and "label->hex", contradicting the settled
path-is-the-id decision. Corrected to id-path.

docs/storage-stack-plan.md

@@ -163,9 +163,9 @@ returns the configured binary; fat's argv parser makes installed mounts a
 function of argv.
 
 **Top risks.** Step 5's blast radius — a parser/argv bug, OR the `/volumes/usb`→
-`/volumes/DANOS` migration missing a fixture/regex, breaks every fat-dependent
-case at once; mitigated by landing the VM half behind fat's hardcoded mounts
-first (step 4) and making the name migration one atomic, complete sweep. The
+id-path migration missing a fixture/regex, breaks every fat-dependent case at
+once; mitigated by landing the VM half behind fat's hardcoded mounts first (step
+4) and making the name migration one atomic, complete sweep. The
 argv blob is 256 bytes (process.zig) — cap emitted mounts and refuse+log on
 overflow. `/system/logs` is now a `volumes.csv` concern: dropping the boot
 identity's rewrite rows silently stops log persistence — ship them by default
@@ -206,7 +206,7 @@ the test disk artifacts.
 **Steps (commits).** (1) `partition.allVolumes` + two-partition host test. (2)
 Tables, behavior-preserving (still one device / one volume). (3) Multi-device +
 multi-partition. (4) Per-volume mount naming via argv — each volume by its
-identity (label→hex, from S2), one per volume, no port-name. (5) fat content-conditional
+id-path (from S2), one per volume, no port-name. (5) fat content-conditional
 boot mounts. (6) Raise `maximum_mounts`. (7) Partitioned-image tool. (8)
 `two-volume` QEMU case. (9) `boot-2nd-partition` case. (10) Adversarial review,
 full suite, docs, memory.