Merge PR #941 dependency into manual compaction stack

# Conflicts:
#	docs/cordis-catalog/services.md
#	docs/core-data-structures/session.i18n.yaml
#	packages/host/apiproxy/README.i18n.yaml
#	packages/host/apiproxy/src/api-proxy.ts
#	packages/ui/tui/src/index.ts

docs/core-data-structures/session.md

@@ -91,6 +91,29 @@ interface SessionEventMap {
    * It is log-only; the latest snapshot reconstructs the request header.
    */
   'request/header': { header: EpochHeader; reason: RequestHeaderReason }
+  /**
+   * Marks the end of a constructor seed. Events before it have smaller seq
+   * values and came from the seed (resume, fork, or replay); this lifecycle
+   * produced none of them. This log-only event is the durable projection of
+   * {@link Session.firstLiveSeq}. Its payload is empty — position and `time`
+   * carry the meaning.
+   *
+   * Locate the LAST one in stored history. A seed already ending in one is not
+   * re-marked, so reopening an untouched session does not grow its log per
+   * pickup and the event need not be at the current `firstLiveSeq`.
+   *
+   * `Session`'s constructor is the only legitimate writer. The invariant
+   * companion deliberately constrains nothing here, so a plugin appending one
+   * would silently classify every live bracket before it as seed history.
+   *
+   * An owner of a standalone open/close bracket (`compact/start` …
+   * `compact/end`) reads it because seed history and live work are otherwise
+   * byte-identical: an unmatched opening marker before this event belongs to
+   * an ended lifecycle, whatever ended it. NOT a liveness signal about other
+   * writers — a concurrently live session holds its own boundary elsewhere,
+   * so tolerating concurrent writers needs a signal beyond the log.
+   */
+  'session/end-seed': Record<string, never>
 }
 ```
 
@@ -320,14 +343,25 @@ declare class Session {
   get id(): SessionId;
   /**
    * The first seq appended IN THIS PROCESS: the length of the constructor
-   * seed (0 without one). Events below it entered through construction —
-   * replay, fork, or resume — and were never published on the `session/event`
-   * firehose (constructor seeds do not emit), so consumers that replay the
-   * log as a publication substitute (telemetry adoption) start here. Distinct
-   * from `header.seedLength`, the DURABLE fork-lineage boundary: a resumed
-   * session's constructor seed is its full stored log, while its header keeps
-   * the original fork value — this field is the in-process construction fact
-   * and is deliberately not persisted.
+   * seed (0 without one). Events with smaller seq values entered through
+   * construction — replay, fork, or resume — and were never published on the
+   * `session/event` firehose (constructor seeds do not emit), so consumers
+   * that replay the log as a publication substitute (telemetry adoption)
+   * start here. Distinct from `header.seedLength`, the DURABLE fork-lineage
+   * boundary: a resumed session's constructor seed is its full stored log,
+   * while its header keeps the original fork value — this field is the
+   * in-process construction fact.
+   *
+   * Not persisted itself: a seeded session projects it into the log as the
+   * `session/end-seed` event, which is what a consumer reading STORED history
+   * reads. Locate the LAST such event, not necessarily one at this seq — a
+   * seed already ending in one is not re-marked, so reopening an untouched
+   * session leaves that event at a smaller seq than `firstLiveSeq`. Prefer
+   * this field in-process: it is exact before the marker reaches storage.
+   *
+   * When this lifecycle appends the marker, it occupies this seq before the
+   * store attaches and therefore does not publish either. Otherwise this seq
+   * holds an ordinary published write.
    */
   readonly firstLiveSeq: number;
   constructor(id: SessionId, seed?: readonly SessionEvent[], header?: SessionHeader);
@@ -508,6 +542,16 @@ A turn encloses one model-loop execution, not the whole session log. Idle inject
 
 The optional `dsh-session/invariant` companion enforces the relations owned by core: turn and step numbering, execution-event enclosure, and same-step tool call/result pairing. Merge-extensible event relations belong to the plugin that declares them, so core does not reject an unknown event merely because no turn is open. See [the standalone-event decision](../../.agents/notes/implemented/simplification/2026-07-28-remove-synthetic-log-only-turns.md).
 
+## The end-seed boundary: `session/end-seed`
+
+A seeded session — resume, fork, or replay — appends this log-only event immediately after its constructor seed, as its first live write. Events before it have smaller seq values and came from the seed. It is the durable projection of `firstLiveSeq`: that field answers where this lifecycle's writes start for a consumer holding the object, while the event answers the same question for one holding only stored bytes. The payload is empty, so position and `time` carry the whole meaning, and it produces no message. `Session`'s constructor is the only legitimate writer.
+
+An empty seed writes nothing, and a seed already ending in `session/end-seed` is not re-marked, so reopening an untouched session does not grow its log per pickup. Locate the LAST `session/end-seed` in stored history rather than assuming one exists at `firstLiveSeq`: after a pickup with no work, the event has a smaller seq than the next lifecycle's `firstLiveSeq`.
+
+It exists because seed history and live work are otherwise byte-identical, which defeats any plugin owning a standalone open/close bracket: an unmatched `compact/start` reads the same whether the writer crashed mid-compaction or is compacting right now. An opening marker before `session/end-seed` came from the constructor seed and belongs to an ended lifecycle, whatever ended it (a crash, a succeeding process, or a fork out of a still-running parent), so its owner may treat it as dead. That covers only brackets *this* session inherited: a concurrently live session holding an open bracket over the same history has its own boundary elsewhere, so tolerating concurrent writers needs a liveness signal beyond the log. Core writes the boundary and reads nothing from it — a bracket's vocabulary stays with its owning plugin, which is why crash repair closes turn/step/tool boundaries and never `compact/*`.
+
+Activity ordering excludes the boundary through `lastActivityTime(events)`: picking a session up is not work, and lazy resume means browsing writes one, so a resume picker or session list ordering by log tail would float every opened session to the top.
+
 ## Plugin-contributed log-only events
 
 A plugin may declaration-merge extra `SessionEventMap` types. These are **log-only**: NOT `SurfaceEventType`s (they carry no `surfaceOp` and contribute nothing to derived history). Their owner decides whether they belong to an open execution turn or may stand between turns, and enforces any relation in its own invariant companion. The full per-event enumeration — core and plugin-contributed alike, with payloads and provenance — is the generated [persistence log event catalog](../persistence-catalog.md); the compaction seam's `compact/*` semantics are discussed on [compaction.md](compaction.md).