docs(log): one dated section per day, and the sweep's lesson learned

The day had three `## 2026-10-21` headings — three logs wearing one date, which is the sprawl the
spec's one-dated-section rule exists to prevent. One date now, one `###` per campaign. `okf-maintenance.md`
states the multi-campaign shape explicitly so nobody has to infer it, and names `AGENTS.md` as the
co-owner of the entry law so an editor changes both.

The new entry records what the dedupe sweep actually taught: an index that restates its own
reference pages becomes the stale authority, and a subagent ledger is a claim until it is re-read
against the file it accuses — most rows returned by the audit fan-out were checkably false, and
half the ledgers never arrived at all. `skills/ecosystem.md` gains the `resource:` frontmatter the
bundle's other externally-sourced pages carry.

Refs #64

omp-docs/references/okf-maintenance.md

@@ -49,7 +49,10 @@ Details: [secret gate](/tools/index.md).
 - **Link, do not duplicate.** Knowledge that outlives the entry belongs on its concept
   page; the entry points there.
 - **One dated section per day** (`## YYYY-MM-DD`), and mention `index.md` whenever a
-  file is added or removed.
+  file is added or removed. Several campaigns on one day share the section: a single
+  `##` date, one `###` per campaign — three `## 2026-10-21` headings is three logs
+  wearing one date. The entry law is also restated in the repo's `AGENTS.md` (the
+  always-loaded tier); change one, change the other.
 
 ### Common Mistakes