Add ACP model-selection strategies for remaining runtimes

[Joncallim]

Context

Forge now has catalog-driven ACP model selection for the Codex CLI and Claude Code ACP runtimes using ACP session config options. Other ACP runtimes may also expose model selection, but they need runtime-specific strategy metadata and smoke tests before Forge should claim that selected models are applied.

Acceptance criteria

• Add model-selection catalog entries only for ACP runtimes that expose an explicit, tested model config option.
• Keep the implementation data-driven through the ACP catalog; do not add adapter-specific branching to the session client.
• For each added runtime, include provider-config tests, session config request tests, and operator-facing UI copy that distinguishes runtime from selected model.
• Runtimes without explicit model selection must continue to show that Forge stores the selected value for clarity but does not pass it to the ACP runtime.

Notes

Initial implemented runtimes: Codex CLI and Claude Code via the Zed ACP adapters.