feat(artifacts): All / Yours / Shared with you tabs on the library

[philmerrell]

PR-2 of the share-inbox pair. #968 gave recipients somewhere to be listed; this is the surface that lists them. Frontend only.

Still dark: with ARTIFACT_SHARE_INBOX_ENABLED off the endpoint 404s, no tabs render, and the library is exactly what it is today.

One row shape, two records

A received artifact is not a LibraryArtifact with extra fields. It has no artifact id and no session to go back to — the share id is the only handle a recipient has on it — and no updatedAt that means anything to them, because that's the owner's clock. Modelling both as one type would invite a template to reach for a field that's structurally absent on half its rows.

So both lists normalize into a LibraryRow carrying a kind discriminator, and the template branches on that and nothing else:

	Owned	Received
Opens	/artifacts/{id}	/shared-artifact/{shareId}
Timestamp	"Updated" (owner's clock)	"Shared" (when you got it)
Actions	Open, Conversation, Rename, Delete	Open
Attribution	—	"Shared by ada@…"

ArtifactThumbnailComponent gains the same discrimination. A recipient can't mint against an artifact id — the owner endpoint builds its DynamoDB key from the session and would 404 — so the source says which credential it is rather than the component inferring it from which fields are populated. Two mint paths, one component, mirroring how ArtifactViewerComponent already serves the owner panel and the recipient page.

The flag reaches the SPA with no new plumbing

listSharedWithMe returns null on 404 — the backend saying the inbox doesn't exist here. Null hides the tabs; [] is a real, empty inbox and says "nothing yet". Collapsing those would either show a permanently empty tab wherever the feature is off, or hide a genuine empty state. Anything that isn't a 404 rethrows: "we couldn't load your inbox" is not "you don't have one".

The two lists load with allSettled, not all. Your own library is the page's reason to exist, so an inbox that 503s must not blank it — the tabs just don't appear, same as when the feature is off. The reverse isn't true, and isn't treated as such.

Smaller calls

• "All" interleaves both lists newest-first. The one place this page sorts, and a deliberate exception to its own no-re-sorting rule: two independently server-ordered lists can't be shown as one without merging on the client. The single-list tabs don't sort at all.
• Search matches the sender on a received row — "who sent me that thing" is at least as likely a starting point as remembering its title.
• "Load more" is inbox-only (the owned endpoint is unpaginated) and stays visible on the All tab, since the merged list is only as complete as what's loaded and hiding the control there would present a partial merge as the whole thing.
• Row keys are prefixed by provenance — an artifact id and a share id come from different key spaces and could otherwise collide into shared DOM.

A contrast defect caught by verifying

I first built the tabs as an underline in primary-accessible. That's a fixed brand colour with no dark variant, so a 2px #0033A0 rule on the #101828 dark surface is nearly invisible — and it passed every unit test. Switched to the filled pill that model-catalog.page.html and this page's own view toggle already use: 10.6:1 on the active pill, and one fewer idiom in the app.

Browser-verified against the compiled stylesheet at 1080px in both themes — tabs, received-card variant, no horizontal overflow.

Tests

2341 passed, +17 from this change (12 tab-behaviour, 3 service contract, 2 mint-path). tsc --noEmit clean.

The one failure in a full run — shared-view.page.spec.ts, a parallel-load timeout its own comment already documents — reproduces on clean develop with these changes stashed, so it's pre-existing and unrelated.

To turn it on

Set CDK_ARTIFACT_SHARE_INBOX_ENABLED=true for the environment and deploy platform.yml. Existing dev shares predate the fan-out and won't appear until re-created; prod has no shares at all, so it's correct from its first one.

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