Split mixed pause-resume changeset so the release plan assembles

PR #976 added a single changeset bumping both @executor-js/execution (in
the fixed release group) and @executor-js/host-mcp (in the changeset ignore
list). Changesets rejects a changeset that mixes ignored and non-ignored
packages, so `changeset version` failed and the Release workflow could not
open the Version Packages PR. Split into two homogeneous changesets, keeping
both changelog entries.

Author: RhysSullivan

.changeset/pause-resume-idempotent-host-mcp.md

@@ -0,0 +1,11 @@
+---
+"@executor-js/host-mcp": patch
+---
+
+Make paused-execution resume reliable: `resume` is now idempotent (a retried
+resume replays the recorded outcome instead of failing with "No paused
+execution"), execution ids are globally unique so a rebuilt engine can never
+re-mint an id a stale client still holds, pauses abandoned by a dead sandbox
+are dropped and their terminal outcome kept for late resumes, and an expired
+or lost pause now returns recovery guidance (re-run execute) instead of a bare
+miss.

.changeset/pause-resume-idempotent.md

@@ -1,6 +1,5 @@
 ---
 "@executor-js/execution": patch
-"@executor-js/host-mcp": patch
 ---
 
 Make paused-execution resume reliable: `resume` is now idempotent (a retried