ver 0.4 effiency pass

echo-memory.plugin.src/skills/echo-memory/references/vault-layout.md

@@ -29,9 +29,10 @@ Mirrors the canonical conventions defined in the vault's own `STRUCTURE.md` and
 │   ├── concepts/  references/  meetings/  source-material/
 │   └── people/        ← <name>.md
 ├── decisions/
-│   ├── by-date/       ← YYYY-MM-DD-<slug>.md (ADR-style)
-│   ├── by-project/    ← mirror by project
+│   ├── by-date/       ← YYYY-MM-DD-<slug>.md (ADR-style) — the canonical home
 │   └── decision-template.md
+│   (decisions/by-project/ exists in the legacy scaffold but is not used —
+│    mirror an ADR into a project's `## Decisions` heading instead)
 ├── reviews/           ← weekly / monthly / quarterly / annual
 ├── archive/           ← notes / projects / imports
 └── _agent/
@@ -44,9 +45,11 @@ Mirrors the canonical conventions defined in the vault's own `STRUCTURE.md` and
     ├── templates/     ← canonical note templates
     ├── outputs/       ← briefs / drafts / summaries / synthesis
     ├── skills/        ← active / archived
-    └── heartbeat/
+    └── heartbeat/     ← single-line pointers (e.g. last-session.md → most-recent session log path)
 ```
 
+**Heartbeat:** `_agent/heartbeat/last-session.md` is a one-line pointer file an agent MAY write at session end (`<session-log-path> @ <ISO-timestamp>`). Reading it at session start is cheaper than listing the sessions directory; use it as a hint, not a source of truth — fall back to the directory listing if it's missing or stale.
+
 **Slug rules:** kebab-case, ASCII only, truncate to ~40 chars.
 
 ---
@@ -97,10 +100,16 @@ not rewrite frontmatter — the append goes after existing content. To change
 
 ### operator-preferences.md (`_agent/memory/semantic/`)
 
-The profile analog. Headings include `Operator`, `Fact / Pattern`, `Evidence`,
-`Recommendation or Implication`, `Review Notes`. Append observed facts under the
-right heading via PATCH. "The operator" is Jason — he is both
-operator and architect of this vault.
+The profile analog. Canonical headings:
+
+- `## Operator` — who Jason is (one paragraph)
+- `## Fact / Pattern` — **promoted, deduped rules.** No date prefix. Timeless.
+- `## Observations` — **timestamped raw observations.** Date-prefixed lines (`- 2026-06-06: ...`). Default landing zone for new evidence.
+- `## Evidence` — citations/links supporting the rules
+- `## Recommendation or Implication` — how the rules should shape behavior
+- `## Review Notes` — confidence / last review date
+
+Append observed facts under `## Observations` by default. Promote to `## Fact / Pattern` (dropping the date) once a pattern stabilizes. "The operator" is Jason — he is both operator and architect of this vault.
 
 ### projects/active/\<slug\>.md
 
@@ -135,12 +144,11 @@ One paragraph, kept fresh via PATCH replace.
 
 ### sessions/YYYY-MM-DD-HHMM-\<slug\>.md
 
-See `session-log-template.md`. Note ECHO uses an **HHMM time component** in the
-filename (unlike a date-only convention).
+See `session-log-template.md`. ECHO uses an **HHMM time component** in the filename — this is **canonical, not optional**. The four-digit local-time component makes filenames lex-sort in true chronological order, which the loading procedure relies on. Older session logs without HHMM exist; leave them alone, but every new one must use the full `YYYY-MM-DD-HHMM-<slug>.md` form.
 
 ### decisions/by-date/YYYY-MM-DD-\<slug\>.md
 
-ADR-style: Context → Decision → Consequences. Mirror a link into `by-project/`.
+ADR-style: Context → Decision → Consequences. If the decision belongs to an existing project, PATCH-append the wikilink into that project's `## Decisions` heading. Don't use `decisions/by-project/` — it's legacy scaffolding that's intentionally left empty.
 
 ### people/\<name\>.md