fix(web): use a circle alert glyph for failed tool calls

[rynfar]

A failed tool call in a live activity row rendered an x glyph. That reads as
"cancelled" rather than "failed", and it sits oddly beside the circle-alert
glyph Pylon already uses for runtime warnings a few rows away.

Swaps the live activity row's failure glyph to circle-alert.

Manual port of upstream pingdotgg/t3code#8840 (8b817cbca) — the commit
conflicts against Pylon's diverged MessagesTimeline.tsx.

One upstream hunk is deliberately not taken. Upstream also added
showFailedIndicator to PlainWorkEntryRow's icon selection. Pylon decoupled
ordinary tool failures from failure glyphs in 4ae51664a ("stop showing red x
summaries for ordinary tool failures"), which reserves alert treatment for severe
failures so a routine lint failure does not look like a broken turn. Applying that
hunk would regress the decision, so only the live activity row changes.

The scoping is confirmed by the tests: only the live-activity assertion needed
updating; the lucide-x assertion covering Pylon's severe-failure path still
passes untouched.

Verified: vp test run --dir apps/web apps/web/src/components/chat/MessagesTimeline.test.tsx
(44 passed), vp run -F @t3tools/web typecheck (exit 0, no errors), vp fmt --check clean.

Reviewed and integrated with Claude Opus 5 in Claude Code.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.6 KiB	13.6 KiB	0 B (0.0%)	15.1 KiB	✅
Codex	Thread snapshot wire	6.9 KiB	6.9 KiB	−4 B (−0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.6 KiB	6.6 KiB	+4 B (+0.1%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	57.2 KiB	57.2 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	21	✅
Claude	Total thread wire	13.6 KiB	13.6 KiB	+21 B (+0.2%)	15.1 KiB	✅
Claude	Thread snapshot wire	6.9 KiB	6.9 KiB	+4 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.6 KiB	6.6 KiB	+17 B (+0.3%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.1 KiB	58.1 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	10	10	0 (0.0%)	21	✅

Baseline: 9ade80d · PR result: 25aed2c · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 109.5 KiB
• Claude decoded thread snapshot: 110.2 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[rynfar]

Closing this — adversarial review showed the change is wrong on its own terms, and the right outcome is to skip #8840 rather than patch it.

The glyph is gated on workEntryDisplayIndicatesToolFailure, which is also true for declined (apps/web/src/session-logic.ts:280). A user-denied tool approval, and a skipped context compaction — ProviderRuntimeIngestion.ts:1370 maps declined to the summary "Context compaction skipped" — both land here. For those rows x is the accurate glyph. The rationale I gave in the PR body, that "x reads as cancelled rather than failed", inverts precisely for the cases that actually were cancelled.

And circle-alert is Pylon's severe-condition glyph, used for tone === "error" and runtime.warning. Painting ordinary failed tool calls with it in the live region erases the distinction 4ae51664a ("stop showing red x summaries for ordinary tool failures") deliberately established — which is the same regression I cited as my reason for not taking upstream's PlainWorkEntryRow hunk. I avoided it on one row and reintroduced it on another.

#8840 is a cosmetic upstream preference that conflicts with a deliberate Pylon decision. Recording it as skipped in the upstream review ledger rather than adopted.

Branch deleted; nothing else depends on it.