fix(macapp): show failed collection loads with inline retry instead of endless skeletons

[dennisonbertram]

Parent: #991

Summary

The app has a typed .failed collection state, but multiple views treat every non-loaded empty collection as “still loading.” A failed request can leave an endless skeleton with no explanation or retry even though ProjectSession.statusMessage recorded an error elsewhere.

Evidence

• macapp/Sources/GoCodeUI/ActivityView.swift:33-37 — failed empty tasks render LoadingPlaceholder.
• ActivityView.swift:45-47 — failed runs with runs == nil render LoadingPlaceholder.
• macapp/Sources/GoCodeUI/SessionsView.swift:24-39 — failed empty conversations render loading rows.
• SessionsView.swift:156-169 — failed rewind-point loads render loading rows.
• macapp/Sources/GoCodeUI/ModelSettingsView.swift:181-186,235-247 — failed provider loads render loading placeholders.
• CollectionLoadState.failed has no failure-presentation contract.

Impact

Network/server failures masquerade as indefinite work. Users cannot tell whether to wait, retry, or fix connectivity, and several affected screens do not render statusMessage at all.

Scope

• Add one shared inline failure state with a concise reason and Retry action.
• Render it for failed empty conversations, tasks, runs, rewind points, providers, profiles, and models.
• When stale data exists, retain it and show a non-blocking refresh-error notice instead of replacing it.
• Keep .idle, .loading, .loaded(empty), and .failed visually and semantically distinct.

Tests first

• Table-driven tests for presentation derived from state + item count + stale-data presence.
• Regression coverage for Activity, Sessions, Checkpoints, and Model Settings production call sites.
• Stub-client tests: 500/transport failure exposes Retry; retry success transitions to loaded content/empty state.

Acceptance criteria

• No .failed collection state renders an indefinite skeleton.
• Every failed collection exposes a visible Retry action and useful next step.
• Stale successful data remains visible during a failed refresh.
• Empty messaging appears only after a successful loaded response.
• Failure text is announced to assistive technology without stealing focus.
• swift test, Swift build, formatting, and strict format lint pass.

[dennisonbertram]

Repair scope for PR #1021 after independent review:

• Add failing-first latest-request tests for catalog, conversations, activity, rewind points, and retries.
• Ensure an older async response cannot overwrite newer state.
• Reconcile the stale-data acceptance criterion so previously loaded rows remain visible with non-blocking refresh failure/retry instead of being replaced.

Settings-specific root-cause work remains pending the separate Settings investigation; shared collection-state behavior stays in this PR.

[dennisonbertram]

PR #1021 repair is pushed at 575b670938821f9db8b5bb096e3956753b0f0e25. #993 now preserves stale rows on refresh failure and renders a compact Retry notice across Sessions, Activity, Models, and Settings. Collection load/reachability coverage and full Swift (303 tests / 55 suites) pass. Native failure/retry smoke remains under #1020.

[dennisonbertram]

PR #1021 exact head afa92d20c7ec10438cbbde4550bb8886e2b0465a repairs partial activity-refresh ownership: if the tracked run terminates while its todo request is in flight, only that stale run-scoped result is discarded; valid tasks/runs still apply and all load states settle. terminalRunOnlyDiscardsItsTodos was observed red then green. Focused review set passes 13 tests / 3 suites; full Swift passes 308 tests / 55 suites.

[dennisonbertram]

PR #1021 exact head 5f76a74a3593a7191a9135b742503658d50ffab2 closes the slow-todo ordering gap: tasks/runs/todos start together, but ready generation-owned tasks/runs apply before awaiting the run-scoped todo. The red regression blocks /todos while proving tasks/runs are already loaded. Full Swift: 313 tests / 55 suites.

[dennisonbertram]

PR #1021 exact head cec0a6654da96c7ef3ab812c489338f72c4fd6db adds pre-mutation ownership checks to reserved startup catalog and conversation refreshes, so a delayed reserved task cannot set newer loaded data back to loading. The source-order regression was red then green. Full Swift: 316 tests / 55 suites.