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-sh4re/src/lib.rs

@@ -751,7 +751,7 @@ pub struct SchedulePromptPayload {
 
 /// Named group of MCP tools an agent may be granted. The harness reads
 /// `HIVE_TOOL_GROUPS` from the environment (a comma-separated list of
-/// snake_case group names written by the meta renderer from per-agent
+/// `snake_case` group names written by the meta renderer from per-agent
 /// config) and expands it to the matching tool names for `--allowedTools`.
 /// When the env var is absent the harness falls back to the flavor default
 /// (`AGENT_DEFAULT` or `MANAGER_DEFAULT`). See `docs/conventions.md::Tool groups`.
@@ -841,7 +841,7 @@ impl ToolGroup {
         Self::Execution,
     ];
 
-    /// The snake_case wire name for this group (matches `serde(rename_all =
+    /// The `snake_case` wire name for this group (matches `serde(rename_all =
     /// "snake_case")` serialisation).
     #[must_use]
     pub fn as_str(self) -> &'static str {
@@ -897,7 +897,7 @@ impl JournalPriority {
 /// which MCP tools the harness exposes to claude).
 ///
 /// Injected into containers as `HIVE_CAPABILITIES` (comma-separated
-/// snake_case) via `meta::render_flake`. The harness reads this to
+/// `snake_case`) via `meta::render_flake`. The harness reads this to
 /// conditionally register capability-gated MCP tools so claude only
 /// sees tools it can actually invoke. See `docs/conventions.md::Capabilities`.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
@@ -925,7 +925,7 @@ pub enum Capability {
 }
 
 impl Capability {
-    /// Canonical snake_case name for this capability (matches serde).
+    /// Canonical `snake_case` name for this capability (matches serde).
     #[must_use]
     pub fn as_str(self) -> &'static str {
         match self {