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/turn.rs

@@ -423,8 +423,7 @@ fn maybe_auto_reset(bus: &Bus) {
     // Compute idle seconds using the same clock as now_unix (unix epoch, i64).
     let now = std::time::SystemTime::now()
         .duration_since(std::time::UNIX_EPOCH)
-        .map(|d| d.as_secs())
-        .unwrap_or(0);
+        .map_or(0, |d| d.as_secs());
     let idle_secs = now.saturating_sub(u64::try_from(last_ended).unwrap_or(0));
     let ttl = cache_ttl_secs();
     if idle_secs < ttl {
@@ -482,7 +481,7 @@ pub fn emit_turn_end(bus: &Bus, outcome: &TurnOutcome) {
 /// snapshot advances (mtime OR file-count change), avoiding the
 /// infinite-401 loop a bare-existence check would produce when stale
 /// credentials are already on disk. Mtime-snapshot resumption rationale
-/// + DirSnapshot two-axis design: see
+/// and `DirSnapshot` two-axis design: see
 /// [`docs/turn-loop.md::The loop`](../../docs/turn-loop.md).
 ///
 /// # Panics