fix(desktop): separate LAN and Tailscale pairing endpoints

[rynfar]

Desktop pairing can label a Tailscale address as LAN when that interface is enumerated first. Separate the endpoints, retain network access on Tailscale-only hosts, and preserve explicit host overrides. Only warn about local-only fallback when it actually occurs.

Adopts upstream #9882 (60e1b73948) and records the partial adoption. Pylon identity and runtime-home behavior are preserved.

Validation: focused desktop exposure tests, desktop typecheck, formatting, and lint pass, including reversed interface order, Tailscale-only hosts, local-only mode, and explicit overrides. No browser or live network settings were changed.

The durable implementation and review record is consolidated in companion #279.

Model: GPT-6 Astra. Harness: Codex.

[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	+12 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	−2 B (−0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.5 KiB	6.5 KiB	+14 B (+0.2%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.5 KiB	56.5 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	8	8	0 (0.0%)	21	✅
Claude	Total thread wire	13.6 KiB	13.8 KiB	+152 B (+1.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	+7 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.6 KiB	6.7 KiB	+145 B (+2.2%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.3 KiB	58.2 KiB	+884 B (+1.5%)	66.4 KiB	✅
Claude	Live turn messages	8	9	+1 (+12.5%)	21	✅

Baseline: de8d090 · PR result: 9400fb2 · 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: 111.2 KiB
• Claude decoded thread snapshot: 111.9 KiB

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