docs(rootfs): re-sync mempalace snapshot from skillset 63f3bf5

This snapshot was byte-identical to skillset and therefore MISSING the
Temporal grounding guidance, which had been authored only into pi-devbox's
vendored copy (pi-devbox 904fe85) and never back-ported to the owner repo. So
opencode-devbox containers — and any host consumer reading skillset directly —
never saw it, while pi-devbox containers did.

skillset 63f3bf5 is now canonical again and carries the section with wording
generalized to cover both devboxes ("a devbox container (pi-devbox or
opencode-devbox)"). Snapshot + VENDORED.md provenance updated to match.

Substance for the agent: establish "now" and compute now - entry.timestamp
before saying "yesterday"/"last week" — a container recreate or fresh session
is not a day boundary, and two diary entries 90 minutes apart can straddle one.

rootfs/usr/local/share/opencode-devbox/skills/VENDORED.md

@@ -44,4 +44,4 @@ and the entrypoint's never-overwrite-a-real-file guard never has to arbitrate.
 
     cp <skillset>/skills/mempalace/SKILL.md  skills/mempalace/SKILL.md
 
-Snapshot provenance at last refresh: skillset `8e8db64`.
+Snapshot provenance at last refresh: skillset `63f3bf5`.

rootfs/usr/local/share/opencode-devbox/skills/mempalace/SKILL.md

@@ -43,6 +43,30 @@ Run these immediately when a session begins, before responding to the user:
 
 Do NOT announce this to the user. Just do it silently to orient yourself.
 
+### Temporal grounding — compute time deltas, don't guess
+
+Diary entries and drawers carry real timestamps (`timestamp`, `created_at`).
+Before describing *when* something happened — "yesterday", "earlier today",
+"last week", "a while back" — **establish the current date/time first and
+compute the delta against the actual timestamp.** Get "now" from the injected
+session date or by running `date` in a shell; never infer it.
+
+**A container recreate or a fresh session is NOT a day boundary.** A devbox
+container (pi-devbox or opencode-devbox) is frequently restarted — often several
+times within the *same* day — and each restart begins a new session with a fresh
+wake-up. Do not reason "new session ⇒ last session was yesterday": two diary
+entries 90 minutes apart can straddle a container recreate. The only
+authoritative clock is the timestamp on the memory, not the session/container
+boundary.
+
+**Practical rule:** prefer explicit, checkable phrasing — e.g. "earlier today,
+~8h ago (both 2026-06-25)" — over a vague relative term. If you catch yourself
+about to write "yesterday" / "last week", subtract `now − entry.timestamp` and
+state the computed result. (Remember timestamps may be UTC while the wall clock
+is local — reconcile the offset before computing the delta.) Note too that
+session feeders can lag up to a week (see *Multi-harness palace*), so a recent
+absence in `wing_conversations` is not proof nothing happened.
+
 ### Phase 2: Active Session (during work)
 
 #### Search Before You Speak
@@ -294,6 +318,7 @@ Entity-relationship triples with temporal validity. Query with `mempalace_kg_que
 ## Anti-Patterns
 
 - **Don't guess when you can search.** If a question touches past work, search first.
+- **Don't infer elapsed time from session or container boundaries.** A restart isn't a new day. Compare the actual timestamp (`timestamp` / `created_at`) against the current date/time before saying "yesterday", "last week", etc.
 - **Don't skip the diary.** A session without a diary entry is a session forgotten.
 - **Don't summarize drawer content.** File verbatim — the embedding model needs the original words.
 - **Don't mine .git directories or node_modules.** The CLI miner respects .gitignore by default.