docs: replace vague provenance prose with recorded facts

packages/subagent/subagent/README.md

@@ -27,7 +27,7 @@ The [subagent family overview](../README.md) maps implementations and model-faci
 
 `SubagentStartRequest.label` is an optional short durable display label for a session-backed one-shot child. Model-facing delegation supplies its existing `description`; lower-level callers need not invent presentation metadata. Continuable starts always carry their own required label. `signal` is required and is the canonical cancellation channel for a one-shot `start`. An abort before publication makes `start()` reject after rollback; an abort after publication cancels the returned run's remaining turn work without hiding its id. The request may also select a model, require structured output, cap delegation depth, restrict child tools, or set a child persona. For a continuable start or follow-up, the caller signal owns lookup, materialization, and admission only until inbox acceptance; afterward the manager owns the Activation independently, so later caller cancellation neither cancels the accepted turn nor disposes the child.
 
-Follow-up authority comes from the exact live direct parent recorded in the child's durable header. Cold resume checks that authority before reconstruction and again in the final no-await inbox-admission span, so a parent unregistered or replaced during materialization cannot authorize delivery. The `source` on a follow-up is durable provenance retained on the delivered message and grants no authority.
+Follow-up authority comes from the exact live direct parent recorded in the child's durable header. Cold resume checks that authority before reconstruction and again in the final no-await inbox-admission span, so a parent unregistered or replaced during materialization cannot authorize delivery. The `source` on a follow-up records who supplied the delivered message and grants no authority.
 
 Same-process requests, descriptors, results, and event payloads are trusted typed values borrowed as immutable. The service does not clone or freeze them; serialization and hostile-input validation belong at actual process, worker, persistence, and model boundaries.
 
@@ -72,13 +72,13 @@ A continuation-managed parent Activation records each child Session id in an `ow
 
 ## Lifecycle events
 
-The service emits a `subagent/start`/`subagent/end` pair for each one-shot run and each resident continuable Activation epoch, so continuable children are observable with the same vocabulary as one-shot runs without exposing whether the manager materialized, woke, or cold-resumed them. For a one-shot start it attaches the result observer before the synchronous `subagent/start`, so even an already-settled child still produces `subagent/start` before `subagent/end`; a continuable epoch that fails before residency emits neither edge. The pair shares a service-minted `runId`; the `local` flag is snapshotted from the provider's exact `localAgent` (always true for a continuable child), so observers never infer run identity or locality from reusable provider/session names. The `provider` field is lifecycle provenance rather than a live-registry claim: an accepted one-shot run may settle after provider removal, and a cold-resumed epoch retains its descriptor's initial provider name without requiring that provider to be registered.
+The service emits a `subagent/start`/`subagent/end` pair for each one-shot run and each resident continuable Activation epoch, so continuable children are observable with the same vocabulary as one-shot runs without exposing whether the manager materialized, woke, or cold-resumed them. For a one-shot start it attaches the result observer before the synchronous `subagent/start`, so even an already-settled child still produces `subagent/start` before `subagent/end`; a continuable epoch that fails before residency emits neither edge. The pair shares a service-minted `runId`; the `local` flag is snapshotted from the provider's exact `localAgent` (always true for a continuable child), so observers never infer run identity or locality from reusable provider/session names. The `provider` field names the provider that started the run or Activation epoch rather than claiming current registration: an accepted one-shot run may settle after provider removal, and a cold-resumed epoch retains its descriptor's initial provider name without requiring that provider to be registered.
 
 Run events are scoped to the delegating parent. Every listener is independently contained: a synchronous throw or rejected returned promise is logged without starving peer listeners or changing the run.
 
 Provider additions and removals also emit `subagent/provider-added` and `subagent/provider-removed`. Consumers such as the model-facing tool use those events because Cordis may load sibling plugins concurrently; configuration order does not prove registration order.
 
-Continuable children do not create `SubagentRun` or Tasks. The continuation manager directly owns one process-local Activation and retained `AgentHandle` per resident child Session, uses the Agent inbox as the only FIFO, and cold-resumes from the durable descriptor. Exact live direct-parent identity authorizes parent-to-child delivery. Exact live child identity authorizes reports; the manager derives the recipient from durable `parentSession`, and `MessageSource` remains provenance rather than authority. Interrupt authority is deliberately wider than delivery authority: a human presents the durable direct-parent address so a live child stays stoppable while its parent Agent is offline, and any exact live ancestor recorded in the Activation's materialization lineage may stop its descendant, because stopping a turn is idempotent and delivers no content.
+Continuable children do not create `SubagentRun` or Tasks. The continuation manager directly owns one process-local Activation and retained `AgentHandle` per resident child Session, uses the Agent inbox as the only FIFO, and cold-resumes from the durable descriptor. Exact live direct-parent identity authorizes parent-to-child delivery. Exact live child identity authorizes reports; the manager derives the recipient from durable `parentSession`, and `MessageSource` records the sender without granting authority. Interrupt authority is deliberately wider than delivery authority: a human presents the durable direct-parent address so a live child stays stoppable while its parent Agent is offline, and any exact live ancestor recorded in the Activation's materialization lineage may stop its descendant, because stopping a turn is idempotent and delivers no content.
 
 When `ctx.sessionProjections` is available, the service registers two projection units. `subagentTiming` resets at each descriptor so a fork seed's ancestor work cannot enter the child's total, then accumulates `turn/start` → `turn/end` active time and retains same-cut `active.since` and `active.through` bounds for an open turn; while that turn remains open, `active.through` follows the latest folded event, giving an inactive consumer a conservative crash bound without mixing in newer session metadata. `subagent` folds the durable identity — mode plus creation label — from `subagent/descriptor` events with the same last-wins reset discipline, so a fork seed's ancestor descriptor stands only until the child's own overrides it; a malformed or unrecognized-version payload folds to the serializable `null` sentinel — indistinguishable from a log with no descriptor, and surviving every JSON push frame so a consumer replaces a stale identity instead of keeping it — and never throws.
 
@@ -105,6 +105,6 @@ No direct invalidation; the named consumers own any request-prefix changes.
 - **No current-turn steering** — continuable messages and waking reports enqueue later turns; neither redirects an open turn.
 - **Wake gap during cancellation convergence** — a waking follow-up accepted after the interrupt signal is issued but before the active driver becomes idle remains queued until another waking send. Issue #1838 owns the agent-loop wake latch, which also affects ordinary session cancellation.
 - **Process-local residency** — the Activation inbox and ownership graph do not coordinate two harness processes; concurrent access to one persistence store still requires a durable mailbox and cross-process lease protocol.
-- **No replay of accepted-but-unlogged messages** — only messages written to the child Session log are reconstructable with their admitted provenance. A crash may lose an accepted initial prompt or follow-up that never reached the log; a later authorized message can cold-resume the child, but the lost message is not replayed automatically.
+- **No replay of accepted-but-unlogged messages** — only messages written to the child Session log are reconstructable with the source that supplied them. A crash may lose an accepted initial prompt or follow-up that never reached the log; a later authorized message can cold-resume the child, but the lost message is not replayed automatically.
 - **No durable report mailbox** — reports require a live direct parent and provide acceptance identity rather than exactly-once delivery or a read receipt.
 - **Lifecycle events are observe-only** — a run-affecting `subagent/end` continuation or decision surface waits for a concrete consumer.