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/bin/hive.rs

@@ -117,7 +117,7 @@ async fn main() -> Result<()> {
 /// Surface a `SYSTEM_SENDER` message in the live event bus + tracing
 /// log. Both agents and the manager receive `QuestionAnswered`,
 /// `ContainerCrash`, reparent notifications, and friends; the parse
-/// + log path is identical. Quiet no-op when `from` isn't
+/// and log path is identical. Quiet no-op when `from` isn't
 /// `SYSTEM_SENDER`.
 fn log_system_event(bus: &Bus, from: &str, body: &str) {
     if from != SYSTEM_SENDER {
@@ -165,7 +165,7 @@ fn consume_continue_sentinel() -> bool {
 
 /// What a `Recv` long-poll returned. Decoupled from the per-role
 /// Response enum so `serve_loop` can pattern-match without seeing
-/// either AgentResponse or ManagerResponse directly.
+/// either `AgentResponse` or `ManagerResponse` directly.
 enum RecvOutcome {
     /// Long-poll returned at least one message; first one is detached.
     Message(hive_sh4re::DeliveredMessage),
@@ -212,7 +212,7 @@ trait Surface {
     fn send_to_parent(socket: &Path, body: String) -> impl Future<Output = ()>;
 
     /// Fire a `Wake { from: "self", body: "continue" }` at our own
-    /// inbox — the request_next_turn sentinel pickup.
+    /// inbox — the `request_next_turn` sentinel pickup.
     fn self_wake(socket: &Path) -> impl Future<Output = ()>;
 
     /// Long-poll the broker for the next message. Wraps the