fix(server): keep malformed usage sources from disconnecting clients

[shivamhwp]

A usage source URL such as localhost:8317 parses with an empty host. Its empty display label fails config-event encoding, disconnecting configuration subscribers and causing the client to reconnect.

Fall back to the source ID when the parsed host is empty, with a readable fallback for a blank ID. Keep the source error visible. This does not repair the configured URL or change management-key handling.

The regression exercises the real usage source service and encodes its config event. All 13 focused usage tests pass; the regression fails on the parent. Targeted lint, format and diff checks pass. Server typecheck passes.

Refs #10193. Stacked on #11298. Internal Fable refinement pending.

GPT-6 via Codex in T3 Code.

[macroscopeapp]

Approvability

Verdict: Approved at c76ed92

Macroscope's review found this PR approvable — The change is a small, isolated server bug fix that supplies valid fallback labels for malformed or hostless usage-source URLs, preventing configuration events from disconnecting clients. Existing labels and normal URL handling remain unchanged, and the added regression test covers the affected cases.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

ℹ️ No successful main baseline artifact is available yet. This run establishes the initial measurement.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	—	13.6 KiB	—	15.1 KiB	✅
Codex	Thread snapshot wire	—	7.0 KiB	—	7.3 KiB	✅
Codex	Live turn WebSocket wire	—	6.5 KiB	—	7.8 KiB	✅
Codex	Live turn WebSocket decoded	—	57.1 KiB	—	66.4 KiB	✅
Codex	Live turn messages	—	10	—	21	✅
Claude	Total thread wire	—	13.6 KiB	—	15.1 KiB	✅
Claude	Thread snapshot wire	—	7.1 KiB	—	7.3 KiB	✅
Claude	Live turn WebSocket wire	—	6.6 KiB	—	7.8 KiB	✅
Claude	Live turn WebSocket decoded	—	57.9 KiB	—	66.4 KiB	✅
Claude	Live turn messages	—	10	—	21	✅

Baseline: unavailable · PR result: c76ed92 · 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: 113.9 KiB
• Claude decoded thread snapshot: 114.6 KiB

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