v3.13.0 — session-mode line (⚙) with per-effort gradient

Added

• Session-mode line (show_mode, default on). A dedicated ⚙ line shows
  how the current turn is configured — ⚙ effort:high · think:on · fast:off · style:default — read straight from Claude Code's stdin (effort.level,
  thinking.enabled, fast_mode, output_style). Each field is dropped when
  absent. cs config set show_mode false to hide.
• Per-effort gradient (mode_gradient, default on). The whole mode line is
  tinted with a static gradient whose palette depends on the effort tier — a
  cool→hot ladder so the level is obvious at a glance: low/auto slate, medium
  blue, high cyan, xhigh amber, max coral, ultracode pink→purple. Static, not
  animated: an external statusLine is re-invoked at ≤1 Hz, so motion can only
  flicker — a stable per-tier sweep is the clean result. cs config set mode_gradient false falls back to plain per-tier text colours.

Fixed

• Reconcile rejects implausible reset times. A bogus far-future resets_at
  (e.g. from corrupt/odd input) used to poison the account-global reconcile
  store permanently — "later reset wins" meant the real, smaller reset could
  never replace it, showing absurd timers like ⏰2283122h. Reconcile now
  ignores resets beyond a window-length-plus-slack and lets a plausible reading
  replace a poisoned one (self-healing).