docs(changeset): state the narrowing's reason as the discriminator argument, and name the two exits that are not healthy

The changeset for this PR justifies leaving every non-stranded parent-resume
exit at `warn`. The justification it now gives is the one this seam can
actually stand behind: those exits carry no `'stranded'` discriminator, and
`'stranded'` is the single exit that journals a repair snapshot — so it is the
single exit an operator can act on, and grading by the engine's own verdict is
what keeps `error` readable rather than skimmed.

That is a claim about what the seam KNOWS, and the changeset now says so, plus
the two exits that are known NOT to have left the parent healthy:

  * a THROWN parent resume carries no discriminator at all, and #15555
    documents a window in which a throw landing between the journal and the
    stamp hides a parent that is genuinely stranded. This seam leaves that arm
    at `warn` deliberately and that card tracks it.
  * the CLAIM-PATH store failure states in its own envelope text that whether
    the suspension was consumed is UNKNOWN, and settles it by retry — which an
    up-bubble has no retrier to perform. "Not consumed" is the guarantee of the
    strict-load store failure alone, never of every store failure.

Text only: no source, no pins and no ledger move, so the measured behaviour and
both mutation legs are untouched. A blanket "the parent is still parked and
resumable" would have read as a platform guarantee across all three exits, and
release notes are built from this file.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XpTx2tbq3pZRYAdoGt6E6Y

Author: claude

.changeset/subflow-bubble-stranded-parent.md

@@ -16,7 +16,20 @@ from the outside, which is the durability class.
 `AutomationResult.status` discriminator: `'stranded'` is reported at `error`,
 naming the parent run and the `restoreConsumedSuspension` verb that repairs it.
 Every other parent-resume failure — a concurrent resume, an unreachable store,
-a thrown resume — stays at `warn` unchanged, because on those exits the parent
-is still parked and resumable.
+a thrown resume — stays at `warn` unchanged, on a narrower ground: those exits
+carry no `'stranded'` discriminator. `'stranded'` is the one exit that journals
+a repair snapshot, so it is the one an operator can act on, and grading by the
+engine's own verdict is what keeps `error` readable.
+
+⚠️ That is a statement about what this seam can KNOW, not a guarantee that
+every other exit left the parent healthy. Two exits are known not to be:
+
+- a **thrown** parent resume carries no discriminator at all, and #15555
+  documents a window in which a throw between the journal and the stamp hides a
+  parent that IS stranded. Left at `warn` deliberately, for that card;
+- the **claim-path** store failure reports, in its own envelope text, that
+  whether the suspension was consumed is UNKNOWN — it relies on a retry to
+  settle it, and an up-bubble has no retrier. ("Not consumed" is the guarantee
+  of the strict-load store failure only, not of every store failure.)
 
 ⚠️ This is the log half only. What the child's resumer is told is unchanged.