feat: extra-usage gating, color hierarchy, test coverage, bug fixes

Add --extra flag (always/on-limit/off) to control when extra-usage
component appears. on-limit shows it only when 5h >= 80% or 7d >= 70%,
keeping the statusline compact until quota pressure makes the budget
actionable. developer theme defaults to on-limit, minimal to off.

Color hierarchy overhaul: path demoted to dim cyan, dirty git branch
pops yellow while clean recedes to dim yellow, time goes plain dim to
reduce color noise, user tier label gets semantic color (MAX=green,
PRO=cyan).

Bug fixes found by code review:
- Color variables used before definition (git info had no ANSI codes)
- format_duration(0) returned "1m" instead of "0m"
- Division by zero when CLAUDE_CONTEXT_LIMIT=0

Also: integer quota percentages (12% not 12.0%), refresh indicator
(~ in flight, ! on error), 1h30m for sessions over 60 minutes,
space between model[1m] and context bar, dead code removal.

85 bats tests (was 56). README rewritten.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: lroolle

CHANGELOG.md

@@ -14,6 +14,37 @@
 - Refreshes expired file-based Claude Code OAuth tokens before quota/profile
   requests.
 
+### Extra Usage Display Mode
+
+New `--extra` flag controls when the extra-usage component appears:
+
+- `always` (default) — show whenever extra usage is enabled
+- `on-limit` — show only when 5h >= 80% or 7d >= 70% (quota under pressure)
+- `off` — never show
+
+The `developer` theme defaults to `on-limit`; `minimal` defaults to `off`.
+
+### UX Refinements
+
+- Quota percentages now display as integers: `5h[12%]` instead of `5h[12.0%]`.
+- Refresh indicator: `~` appears after quota cluster when an API fetch is in
+  flight, `!` when the last fetch failed and data may be stale. Extra usage
+  has its own independent indicator (separate API call).
+- Duration shows hours for long sessions: `1h30m` instead of `90m`.
+- Added space between model suffix and context bar to prevent visual confusion:
+  `opus4.6[1m] [█░░░░░26%]` instead of `opus4.6[1m][█░░░░░26%]`.
+- Removed dead `add_component_no_space` and `format_usage_bar` functions.
+- Fixed `format_duration(0)` returning "1m" instead of "0m".
+- Fixed color variables used before definition (git info, path had no color).
+- Guarded context percentage against division by zero (`CLAUDE_CONTEXT_LIMIT=0`).
+
+### Color Hierarchy
+
+- Path demoted to dim cyan — frees visual weight for primary signals.
+- Git branch: dirty=yellow (pops), clean=dim yellow (recedes).
+- Time: plain dim instead of dim cyan — less color noise.
+- User tier label gets color: MAX=green, PRO=cyan, ENT/TEAM=dim cyan.
+
 ### Documentation
 
 - Documented the extra-usage component, API behavior, and updated README preview