feat: add environment sections, visual enhancements, enhanced tools/beads, and /clear detection

The feature layer that builds on the new infrastructure modules. Adds
4 new environment-aware sections, rewrites the tools/beads/turns sections,
introduces gradient sparklines and block-style context bars, and wires
/clear detection into the main binary.

New sections (4):
  cloud_profile — Shows active cloud provider profile from env vars
    ($AWS_PROFILE, $CLOUDSDK_CORE_PROJECT, $AZURE_SUBSCRIPTION_ID).
    Provider-specific coloring (AWS orange, GCP blue, Azure blue).

  k8s_context — Parses kubeconfig for current-context and namespace.
    Minimal YAML scanning (no yaml dependency). 30s TTL cache.
    Shows "context/namespace" with split coloring.

  python_env — Detects active virtualenv ($VIRTUAL_ENV) or conda
    ($CONDA_DEFAULT_ENV, excluding "base"). Shows just the env name.

  toolchain — Detects Rust (rust-toolchain.toml) and Node.js (.nvmrc,
    .node-version) versions. Compares expected vs actual ($RUSTUP_TOOLCHAIN,
    $NODE_VERSION) and highlights mismatches in yellow.

Tools section rewrite:
  Progressive disclosure based on terminal width:
    - Narrow: just the count ("245")
    - Medium: count + last tool name ("245 tools (Bash)")
    - Wide: per-tool color-coded breakdown ("245 tools (Bash: 84/Read: 35/...)")
  Adaptive width budgeting: breakdown reduces tool count until it fits
  within 1/3 of terminal width. Color palette priority: config > terminal
  ANSI palette (via OSC 4) > built-in Dracula palette.

Beads section rewrite:
  Switched from `br ready --json` to `br stats --json` to show all
  statuses. Now renders multi-status breakdown: "3 ready 1 wip 2 open"
  with per-status visibility toggles in config.

Turns section:
  Falls back to transcript-derived turn count when cost.total_turns is
  absent. Requires at least one data source to render (vanishes when
  no session data exists at all).

Visual enhancements:
  trend.rs:
    - append_delta(): tracks rate-of-change (delta between cumulative
      samples) so sparklines show burn intensity, not monotonic growth
    - sparkline(): now renders exactly `width` chars with left-padding
      for missing data. Baseline (space) vs flatline (lowest bar) chars.
    - sparkline_colored(): per-character gradient coloring via colorgrad,
      returns (raw, ansi) tuple for layout compatibility.

  context_bar.rs:
    - Block style: Unicode full-block fill + light-shade empty chars
    - Per-character green->yellow->red gradient for block style
    - Classic style preserved (= and - chars) with single threshold color
    - Configurable fill_char/empty_char overrides

  context_trend + cost_trend:
    Switched to append_delta for rate-based sparklines. Gradient coloring
    with green->yellow->red via sparkline_colored().

  format.rs:
    Background color support via resolve_background(). Accepts named
    colors, hex, and palette refs. Applied as ANSI bg wrap around section
    output, preserving foreground colors.

  layout/mod.rs:
    - Separator styles: text (default), powerline (Nerd Font), arrow
      (Unicode), none (spaces). Powerline auto-falls-back to arrow when
      glyphs disabled.
    - Placeholder support: when an enabled section returns None (no data),
      substitutes a configurable placeholder character (default: box-draw)
      to maintain layout stability during justify/flex.

Section refinements:
  cost, cost_velocity, token_velocity, duration, tokens_raw — now show
  zero/baseline values instead of hiding entirely. This prevents layout
  jumps when sessions start or after /clear.

  context_usage — uses current_usage fields (input_tokens +
  cache_creation + cache_read) for precise token counts instead of
  percentage-derived estimates. Shows one decimal place on percentage.

  metrics.rs — prefers total_api_duration_ms over total_duration_ms for
  velocity calculations (active processing vs wall clock with idle time).
  Cache efficiency now divides by total input (not just cache tokens).

Config additions (config.rs):
  SeparatorStyle enum (text/powerline/arrow/none), BarStyle enum
  (classic/block), gradient toggle on trends + context_bar, background
  and placeholder on SectionBase, tools breakdown config (show_breakdown,
  top_n, palette), 4 new section structs.

Main binary (/clear detection + wiring):
  detect_clear() — watches for significant context usage drops (>15%
  to <5%, >20pp drop) to identify /clear. On detection: saves transcript
  offset so derived stats only count post-clear entries, flushes trend
  caches for fresh sparklines.

  resolve_transcript_stats() — cached transcript parsing with 5s TTL,
  respects clear offset, skipped when cost already has tool counts.

  resolve_terminal_palette() — cached palette detection with 1h TTL.

  Debug: CLAUDE_STATUSLINE_DEBUG env var dumps raw input JSON to
  /tmp/claude-statusline-input.json. dump-state now includes input data.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/config.rs

@@ -45,6 +45,7 @@ impl Default for LayoutValue {
 #[serde(default)]
 pub struct GlobalConfig {
     pub separator: String,
+    pub separator_style: SeparatorStyle,
     pub justify: JustifyMode,
     pub vcs: String,
     pub width: Option<u16>,
@@ -75,6 +76,7 @@ impl Default for GlobalConfig {
     fn default() -> Self {
         Self {
             separator: " | ".into(),
+            separator_style: SeparatorStyle::Text,
             justify: JustifyMode::Left,
             vcs: "auto".into(),
             width: None,
@@ -121,6 +123,24 @@ pub enum ColorMode {
     Never,
 }
 
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+pub enum SeparatorStyle {
+    #[default]
+    Text,
+    Powerline,
+    Arrow,
+    None,
+}
+
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum BarStyle {
+    Classic,
+    #[default]
+    Block,
+}
+
 #[derive(Debug, Deserialize)]
 #[serde(default)]
 pub struct Breakpoints {
@@ -172,6 +192,8 @@ pub struct SectionBase {
     pub pad: Option<u16>,
     pub align: Option<String>,
     pub color: Option<String>,
+    pub background: Option<String>,
+    pub placeholder: Option<String>,
 }
 
 impl Default for SectionBase {
@@ -186,6 +208,8 @@ impl Default for SectionBase {
             pad: None,
             align: None,
             color: None,
+            background: None,
+            placeholder: Some("\u{2500}".into()),
         }
     }
 }
@@ -219,6 +243,10 @@ pub struct Sections {
     pub time: TimeSection,
     pub output_style: SectionBase,
     pub hostname: SectionBase,
+    pub cloud_profile: SectionBase,
+    pub k8s_context: CachedSection,
+    pub python_env: SectionBase,
+    pub toolchain: SectionBase,
 }
 
 #[derive(Debug, Deserialize)]
@@ -356,6 +384,10 @@ pub struct ContextBarSection {
     #[serde(flatten)]
     pub base: SectionBase,
     pub bar_width: u16,
+    pub bar_style: BarStyle,
+    pub gradient: bool,
+    pub fill_char: Option<String>,
+    pub empty_char: Option<String>,
     pub thresholds: Thresholds,
 }
 
@@ -369,6 +401,10 @@ impl Default for ContextBarSection {
                 ..Default::default()
             },
             bar_width: 10,
+            bar_style: BarStyle::Block,
+            gradient: true,
+            fill_char: None,
+            empty_char: None,
             thresholds: Thresholds {
                 warn: 50.0,
                 danger: 70.0,
@@ -492,6 +528,7 @@ pub struct TrendSection {
     #[serde(flatten)]
     pub base: SectionBase,
     pub width: u8,
+    pub gradient: bool,
 }
 
 impl Default for TrendSection {
@@ -502,6 +539,7 @@ impl Default for TrendSection {
                 ..Default::default()
             },
             width: 8,
+            gradient: true,
         }
     }
 }
@@ -512,6 +550,7 @@ pub struct ContextTrendSection {
     #[serde(flatten)]
     pub base: SectionBase,
     pub width: u8,
+    pub gradient: bool,
     pub thresholds: Thresholds,
 }
 
@@ -523,6 +562,7 @@ impl Default for ContextTrendSection {
                 ..Default::default()
             },
             width: 8,
+            gradient: true,
             thresholds: Thresholds::default(),
         }
     }
@@ -534,6 +574,13 @@ pub struct ToolsSection {
     #[serde(flatten)]
     pub base: SectionBase,
     pub show_last_name: bool,
+    /// Show per-tool breakdown (e.g., "Bash:84 Read:35 Edit:34").
+    pub show_breakdown: bool,
+    /// Max number of tools to show in breakdown (0 = all).
+    pub top_n: usize,
+    /// Rotating color palette for tool names (hex strings, e.g. "#8be9fd").
+    /// Falls back to built-in Dracula palette when empty.
+    pub palette: Vec<String>,
     pub ttl: u64,
 }
 
@@ -546,6 +593,9 @@ impl Default for ToolsSection {
                 ..Default::default()
             },
             show_last_name: true,
+            show_breakdown: true,
+            top_n: 7,
+            palette: Vec::new(),
             ttl: 2,
         }
     }