Three UX gaps on the portal-bar closed in one pass plus a defensive
fix on the C tier's heap probe:
* Overwrite guard — saving with an existing name asks 'overwrite?'
with the existing entry's tier + savedAt. Rename via dbl-click on
the chip label; same overwrite guard applies on rename.
* Export / import — a ⇣ icon on each chip downloads it as
<name>.portal.json (opaque blob for c/python, replay-inputs for
asm). A 📁 import button on the portal-bar accepts a .portal.json
file via hidden <input type="file">; collisions prompt overwrite,
decline auto-suffixes (baseName-2, -3, …) so importing a 2nd copy
always lands somewhere.
* Cross-tab restore — a 📂 this tab / 🌐 all tabs toggle switches
the chip strip between the active tab's checkpoints and every
tab's. Global chips render as 'name · tabName' with a dashed
border; click restores the snapshot into the active tab (the
saved cp is passed through restoreCheckpoint's new sourceCp
argument so the chip doesn't need a checkpoints[name] match on
the active tab). Edit/delete are hidden in global mode — the
user switches to the owning tab to manage chips.
* heapStats defensive — wasm/c/lumbda-c.loader.js now returns null
when module.HEAPU8 isn't live yet (caught by the heap poll firing
during the tiny window between tier reboot and Module init), so a
restore no longer surfaces 'Cannot read properties of undefined
(reading byteLength)' as a TypeError.
Smoke-tested headlessly: overwrite confirm fires with the expected
message; rename via dblclick swaps the label; ⇣ produces a download
named '<name>.portal.json'; toggle shows both tabs' chips with the
'· tabName' annotation; import round-trips back into the receiving
tab. Zero page errors across the full flow.
russell@unturf.com
2b46c1b79e