feat: transport resolved reasoning effort

bin/install.js

@@ -2360,6 +2360,10 @@ Direct mapping:
   GSD embeds the resolved per-agent model directly into each agent's \`.toml\`
   at install time so \`model_overrides\` from \`.planning/config.json\` and
   \`~/.gsd/defaults.json\` are honored automatically by Codex's agent router.
+- Resolved \`reasoning_effort="low|medium|high|xhigh"\` → pass \`reasoning_effort\`
+  to \`spawn_agent\` when the runtime/tool supports it. Omit missing, empty,
+  inherited, or unsupported values; do not invent one-off effort literals in
+  workflow prose.
 - \`fork_context: false\` by default — GSD agents load their own context via \`<files_to_read>\` blocks
 - \`Task(isolation="worktree")\` / \`Agent(isolation="worktree")\` → no direct Codex mapping.
   Codex \`spawn_agent\` does not create or bind a git worktree automatically.