Desktop: show the model in use for all hosted harnesses as chips in the agent list #899

Problem

In the desktop app's hosted-agent list, only Pi shows the model in use. All supported harnesses should show their model, rendered as a chip like the web UI.

Findings

• The rail already renders row.Model for every vendor when non-empty (RailSessionViewModel.Sub). Pi is the only vendor that populates a model on a default launch, because its RPC handshake reports the running model (src/Capacitor.Cli.Daemon/Harness/Pi/PiRpcHostedAgentRuntime.cs), captured as ResolvedModel at registration (AgentOrchestrator.cs:2401).
• Claude/Codex (PTY) and the ACP vendors leave AgentInstance.Model blank on a default launch. Codex resolves its real model but reports it to the server registry only (AgentOrchestrator.cs:2644), not the local status frame.
• Web UI renders the model as a single uniform info-tint chip (not per-model colour): kcap-server CompactStatsRow.razor (hk-chip-model).

Proposed change

• UI: render the model as an info-tint chip beside the vendor chip in the rail, shown when non-empty.
• Daemon (best-effort resolution): also update the local AgentInstance.Model for Codex when it resolves; capture the ACP vendors' current/default model from their handshake. Selected models already flow for all vendors once launcher model selection lands (see model-selection issue). Claude PTY default launches (no model requested) may remain blank — accepted as the best-effort gap.

Acceptance

• On a launch where a model is selected, the model chip appears for every vendor.
• On default launches, the model chip appears for Pi (unchanged), Codex, and ACP vendors where the handshake exposes it.