ci: add GitHub Actions workflows with semantic-release auto-versioning

chore: fix all 702 clippy warnings across codebase
- auto-fix 475 via cargo clippy --fix
- fix remaining 227 manually: uninlined_format_args, redundant_closure, match_same_arms,
  underscore_binding, format_push_string, items_after_statements, needless_pass_by_value,
  clone_on_copy, case_sensitive_extension, single_match/let-else, write_with_newline,
  and other clippy lints

src/app/subagent/context.rs

@@ -37,10 +37,10 @@ pub struct SubagentContext {
 ///
 /// Return: a context with empty `system_prompt`, empty `workspaces`,
 /// empty `session_dir`, resolved `max_steps`, and the resolved allowed-tool list.
-pub fn build_subagent_context(def: AgentDefinition) -> SubagentContext {
+pub fn build_subagent_context(def: &AgentDefinition) -> SubagentContext {
     let allowed_tools = def.allowed_tools.clone().unwrap_or_else(|| {
         if def.role == "reviewer" {
-            REVIEWER_ALLOWED.iter().map(|s| s.to_string()).collect()
+            REVIEWER_ALLOWED.iter().map(std::string::ToString::to_string).collect()
         } else {
             Vec::new()
         }