fix: streaming robustness — OpenAI parsing, error detection, reasoning content

Improves SSE parsing with raw JSON error detection, HTML response detection (for misconfigured endpoints), thinking/reasoning content from provider-specific delta fields, #[serde(default)] on streaming types for lenient deserialization, compact session boundary guard, and /team slash command. Adds install.sh convenience script.

rust/crates/commands/src/lib.rs

@@ -1472,6 +1472,7 @@ pub fn validate_slash_command_input(
         }
         "plan" => SlashCommand::Plan { mode: remainder },
         "review" => SlashCommand::Review { scope: remainder },
+        "team" => SlashCommand::Team { action: remainder },
         "tasks" => SlashCommand::Tasks { args: remainder },
         "theme" => SlashCommand::Theme { name: remainder },
         "voice" => SlashCommand::Voice { mode: remainder },