fix(#999): resolve all clippy warnings across the workspace

All crates now pass `cargo clippy --workspace -- -D warnings` cleanly.

Fixes span six crates (hive-sh4re, hive-ag3nt, hive-c0re, hive-forge,
hive-priv, hive-matrix-mcp was already clean):

- doc_markdown: wrap snake_case, type names, constants in backticks
- collapsible_if / collapsible_match: fold nested ifs into let-chains
- duration_suboptimal_units: Duration::from_secs(N) → from_mins/from_hours
- implicit_hasher: allow on HashMap-param fns where generalization is risky
- items_after_statements: hoist use to function tops
- map(f).unwrap_or(x) → map_or(x, f); map(f).unwrap_or_else(g) → map_or_else
- is_ok_and / is_none_or in place of map().unwrap_or(bool)
- needless_continue: {} instead of continue in loop match arms
- match_same_arms: Ok(None) | Err(_) merged
- format_push_str: write!() instead of push_str(&format!())
- while let replaces loop { let Some(..) = x else { break } }
- struct_excessive_bools / dead_code: allow on purpose-built structs
- too_many_lines / too_many_arguments: allow where refactor not worth it
- unused_async: remove async from poll_once in bash_runner
- needless_borrow: fix &repo deref in hive-forge comments verb
- cast_possible_truncation: allow u64→usize in fetch_tail

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hive-ag3nt/src/bash_runner.rs

@@ -229,7 +229,7 @@ async fn run_loop(socket: PathBuf) {
     let claimed: Arc<Mutex<HashSet<String>>> = Arc::new(Mutex::new(HashSet::new()));
 
     loop {
-        poll_once(&socket, &claimed).await;
+        poll_once(&socket, &claimed);
         tokio::time::sleep(POLL_INTERVAL).await;
     }
 }
@@ -258,7 +258,7 @@ async fn mark_interrupted(socket: &Path) {
     }
 }
 
-async fn poll_once(socket: &Path, claimed: &Arc<Mutex<HashSet<String>>>) {
+fn poll_once(socket: &Path, claimed: &Arc<Mutex<HashSet<String>>>) {
     let Ok(rd) = std::fs::read_dir(tasks_dir()) else { return };
     for entry in rd.flatten() {
         let path = entry.path();