Split subsession inspection into two tools: check_subsession gives a quick
glance (status + latest assistant output), while read_subsession reads through
a child's transcript with role/content filters, full-content substring search
(including tool-call args), optional per-value maxChars truncation that flags
clipped parts, includeToolArgs, and pagination.
Filtering and search run on full untruncated content; truncation is an explicit,
caller-owned final projection (no default) so a narrow read never silently hides
a match. Empty page-windows are distinguished from zero-match results.
Add spawn_subsession / list_subsessions / read_subsession tools that let an
agent start child sessions it stays attached to: the child records its parent
in the session tree, the parent is notified (as a system-authored custom
message that wakes an idle parent and queues behind in-flight work) when the
child stops working, and the parent can inspect children's status and result.
Gated behind a beta flag, off by default, mirroring spawnSessions: enable via
PI_WEB_SUBSESSIONS, the subsessions config key, or the Settings toggle. Also
requires spawnSessions.
Also fix the release skill so the version step resyncs package-lock.json
(npm install --package-lock-only) and the commit step refuses a release where
package.json and package-lock.json versions disagree.