chore(core): tidy review nits — alphabetical lib.rs, import placement, docstring

End-of-phase cleanup of items flagged across review passes for tasks
1.1, 1.2, and 1.3:

1. crates/core/src/lib.rs: pub mod power moved to alphabetical
   position (between paths and process_watch).
2. crates/core/src/power.rs: use statements moved to top of file
   (above the PowerState enum) per Rust convention.
3. crates/core/src/power.rs: parse_power_state_from_dir docstring
   tightened to acknowledge that read_dir.flatten() silently skips
   per-entry errors. Theoretical hazard only on world-readable
   sysfs, but the previous wording overstated the guarantee.

No behavioural change. All 40 magnotia-core tests still green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/core/src/lib.rs

@@ -3,9 +3,9 @@ pub mod error;
 pub mod hardware;
 pub mod model_registry;
 pub mod paths;
+pub mod power;
 pub mod process_watch;
 pub mod recommendation;
-pub mod power;
 pub mod tuning;
 pub mod types;
 

crates/core/src/power.rs

@@ -7,6 +7,11 @@
 //! now; native probes (IOPSGetProvidingPowerSourceType,
 //! GetSystemPowerStatus) are deferred.
 
+use std::fs;
+use std::path::Path;
+use std::sync::{Mutex, OnceLock};
+use std::time::{Duration, Instant};
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum PowerState {
     OnAc,
@@ -14,11 +19,6 @@ pub enum PowerState {
     Unknown,
 }
 
-use std::fs;
-use std::path::Path;
-use std::sync::{Mutex, OnceLock};
-use std::time::{Duration, Instant};
-
 /// Parse a `/sys/class/power_supply/`-style directory and decide
 /// whether the machine is on AC, on battery, or in an unknown state.
 ///
@@ -27,9 +27,15 @@ use std::time::{Duration, Instant};
 /// - Else any entry with `type == Battery` → OnBattery.
 /// - Else → Unknown.
 ///
-/// Failures (missing dir, unreadable files, malformed contents) all
+/// Top-level failures (missing dir, unreadable supply_dir) return
-/// fall through to Unknown rather than panicking. `Unknown` is treated
+/// Unknown without panicking. Per-entry failures (unreadable
-/// as `OnAc` by the caller, which preserves today's pre-clamp
+/// `type`/`online` file inside an individual supply, e.g. permission
+/// denied or non-UTF-8 content) cause that entry to be silently
+/// skipped via `read_trimmed().unwrap_or_default()` — which on a
+/// stuck-AC machine could produce OnBattery if the Mains entry was
+/// the unreadable one. In practice sysfs entries are world-readable,
+/// so this is a theoretical hazard rather than a real one. `Unknown`
+/// is treated as `OnAc` by the caller, preserving today's pre-clamp
 /// behaviour on platforms or distros where the probe doesn't fire.
 pub fn parse_power_state_from_dir(supply_dir: &Path) -> PowerState {
     let read_dir = match fs::read_dir(supply_dir) {