feat: redesign bubble as two-bar rounded rect, finish port wiring

Bubble shape changes from circle to rounded rectangle showing two stacked
horizontal bars — top: session (5h), bottom: weekly (7d) — each followed
by a right-aligned "X% · Yh Zm" string (percent + countdown).

Bubble surface:
- BubbleConfig/BubbleState carry session+weekly percents and texts (mirrors
  PanelData); update_percentage renamed to update_data
- Aspect ratio fixed at 3:1; size_logical is interpreted as width with
  height derived. Clamp is 120..360 (was 32..128 square)
- Hit-testing uses a rounded-rect predicate (point_in_rounded_rect) shared
  with the alpha mask so paint and click area can't drift
- New rgb_to_dib helper for direct DIB writes — BI_RGB 32bpp stores B,G,R,X
  in memory which is the opposite of COLORREF. The previous code wrote
  COLORREF-packed u32 straight into DIB pixels; invisible while every color
  was gray, but the new orange/red bar fills would have rendered blue
- bar_h capped at h/4 (range 6..18) so the text font derived from it stays
  small enough that "100% · 23h" fits in right_text_w (= 6×bar_h, min 56);
  the first iteration had a 19-px font in a 60-px column and ellipsized
  away the countdown
- Initial session_text/weekly_text seeded with "…" so the bubble has
  visible feedback during the first poll instead of two empty grey tracks

Compile + cleanup needed to make the port build at all:
- Color::from_hex added back as an infallible wrapper around parse_hex
  (15 call sites in bubble.rs/panel.rs assumed the old infallible API)
- Color::to_colorref → into_colorref at 5 call sites
- GetModuleFileNameW added to the LibraryLoader import in bubble.rs
- usage::Error gains Creds(#[from] creds::Error) so `?` works in the
  Anthropic and ChatGPT providers
- FlattenBoxed::flatten renamed to flatten_box — the std Option::flatten
  was shadowing it and yielding Option<Box<T>> instead of Option<T>
- PanelState marked unsafe Send (HWND has *mut c_void; state is only
  touched from the UI thread, Mutex is for OnceLock satisfaction)
- Crate-level #![allow(dead_code)] for in-progress port API surface
  (creds, usage, update, os::dpi); unused pub-use re-exports removed

App wiring:
- propagate_to_ui now feeds both windows + their formatted texts into
  update_data (was a single percent)

src/usage/anthropic.rs

@@ -8,7 +8,7 @@ use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 use serde::Deserialize;
 
-use crate::creds::{CredentialSource, Locator};
+use crate::creds::Locator;
 use crate::net::Client;
 use crate::usage::{headers, Error, ProviderId, UsageProvider, UsageWindows, Window};
 

src/usage/chatgpt.rs

@@ -7,7 +7,7 @@ use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 use serde::Deserialize;
 
-use crate::creds::{CredentialSource, Locator};
+use crate::creds::Locator;
 use crate::net::Client;
 use crate::usage::{Error, ProviderId, UsageProvider, UsageWindows, Window};
 
@@ -67,16 +67,16 @@ impl UsageProvider for ChatGptProvider {
 }
 
 fn envelope_to_windows(envelope: Envelope) -> Option<UsageWindows> {
-    let rl = envelope.rate_limit.flatten()?;
+    let rl = envelope.rate_limit.flatten_box()?;
     Some(UsageWindows {
         primary: rl
             .primary_window
-            .flatten()
+            .flatten_box()
             .map(window_from)
             .unwrap_or_default(),
         secondary: rl
             .secondary_window
-            .flatten()
+            .flatten_box()
             .map(window_from)
             .unwrap_or_default(),
     })
@@ -114,12 +114,14 @@ struct ApiWindow {
     reset_at: i64,
 }
 
-// Helpers used to make `Option<Option<Box<…>>>` flatten cleanly.
+// Helpers used to make `Option<Option<Box<…>>>` flatten cleanly. We can't
+// reuse the std `Option::flatten` name — the inherent method (which returns
+// `Option<Box<T>>`) would shadow this trait method.
 trait FlattenBoxed<T> {
-    fn flatten(self) -> Option<T>;
+    fn flatten_box(self) -> Option<T>;
 }
 impl<T> FlattenBoxed<T> for Option<Option<Box<T>>> {
-    fn flatten(self) -> Option<T> {
+    fn flatten_box(self) -> Option<T> {
         self.and_then(|inner| inner.map(|b| *b))
     }
 }

src/usage/mod.rs

@@ -12,7 +12,7 @@ pub mod registry;
 pub mod types;
 
 pub use registry::Registry;
-pub use types::{ProviderId, ProviderSnapshot, UsageWindows, Window};
+pub use types::{ProviderId, UsageWindows, Window};
 
 #[derive(Debug, thiserror::Error)]
 pub enum Error {
@@ -24,6 +24,8 @@ pub enum Error {
     TokenExpired,
     #[error("network: {0}")]
     Network(#[from] crate::net::Error),
+    #[error("credentials: {0}")]
+    Creds(#[from] crate::creds::Error),
     #[error("unexpected response shape: {0}")]
     BadResponse(String),
 }