fix(ysync): review bugs 01–07 — listener registration, pad nets, child removals, dirty-set emit, targeted rebaseline, seed arbitration, stale hook (doc 17)

All seven ysync-review bugs fixed and verified; every repro's expected-fail
marker removed (they now run as regression tests). Also fixes two bugs found
while verifying (doc 17 F5/F6): file-seeded Y bodies are re-upserted in the
editor's serialization (doc-16 F4 was an artifact of bug 01), and the
0008-era "asyncify-fragile envelope parse" was really wrapInBoardEnvelope
emitting display layer names — canonical LSET::Name() fixes track/via/zone
v2 applies; makeFromBlob now logs parse errors instead of swallowing them.

Verified: shared 98, standalone collab 37, ysync e2e 20/20 (chromium),
collab regression set 21 passed / 3 pre-existing skips (firefox).

Bumps: kicad (board_commit child-removal listener notification),
web/pcbjam-shared (slot prune + arbitrated seed).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JgThWXtdvrYLK47EDFoGdq

docs/features/ysync-review/02-bug-footprint-blob-zeroes-pad-nets.md

@@ -1,7 +1,7 @@
 # Bug 02 — Footprint blobs zero pad net codes; net data loss propagates to peers, the Y.Doc, and materialized files
 
 **Severity:** high (silent, converging data corruption on boards with nets)
-**Status:** open — runtime-CONFIRMED 2026-07-03: the snapshot blob carries the pads
+**Status:** FIXED 2026-07-03 — see [17](17-fixes-bugs-01-07.md) (batch 2)
 with `(net 1 "SIG")` stripped (repro below)
 
 ## Where