feat(usage): plan usage limits header chip via statusLine telemetry

Surface Claude subscription plan usage limits (5-hour rolling + 7-day
weekly: percent used + reset time) in the header, opt-in via App Settings
→ Display → "Plan Usage Limits" (default OFF, no behavior change when off).

A Codeman-managed Claude statusLine exporter forwards the rate_limits JSON
to a new auth-exempt POST /api/status-telemetry (same loopback + hook-secret
gate as /api/hook-event); parsed telemetry broadcasts over SSE
session:statusTelemetry to a header chip (amber >=80%, red >=95%, reset
times on hover). The exporter prints the same summary back as the
in-terminal footer (print-through).

- src/usage-telemetry.ts: pure parser/formatter (epoch-sec -> ms, clamp,
  change signature) + test/usage-telemetry.test.ts
- hooks-config.ts: generateStatusLineCommand + applyStatusLineConfig
  (add/remove; never clobbers a user's own statusLine)
- session-routes.ts: inject gate (Claude-only, Codeman-managed cases),
  driven by create-payload statusLineTelemetry (session-ui.js)
- schemas.ts: StatusTelemetrySchema + showPlanUsageLimits + payload field
- frontend: header chip, applyHeaderVisibilitySettings toggle,
  renderIndexHtml strip, _onSessionStatusTelemetry handler

Schema empirically confirmed against Claude Code 2.1.177 (Claude Max):
only five_hour/seven_day windows exist (no Opus-weekly field); rate_limits
is absent before the first API response and for non-subscriber auth. Design
+ verification method in docs/usage-limits-display-plan.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/web/public/styles.css

@@ -1107,6 +1107,7 @@ body.solo-mode .header-system-stats,
 body.solo-mode .header-tokens,
 body.solo-mode .btn-notifications,
 body.solo-mode .btn-multimonitor,
+body.solo-mode .header-plan-usage,
 body.solo-mode .btn-lifecycle-log {
   display: none !important;
 }
@@ -8321,6 +8322,38 @@ kbd {
   display: none !important;
 }
 
+/* Plan-usage chip (App Settings → Display → "Plan Usage Limits"). Shows the
+   live 5-hour + weekly plan limits parsed from the Claude statusline. Hidden by
+   default via the marker class below; the server strips it at render when the
+   setting is on and the client toggles it live on save. */
+.header-plan-usage {
+  display: inline-flex !important;
+  align-items: center;
+  height: 22px;
+  padding: 0 0.5rem;
+  border-radius: 11px;
+  font-size: 0.7rem;
+  font-weight: 500;
+  font-family: 'SF Mono', Monaco, monospace;
+  color: var(--text-dim);
+  background: rgba(255, 255, 255, 0.05);
+  border: 1px solid rgba(255, 255, 255, 0.08);
+  white-space: nowrap;
+  cursor: default;
+}
+.header-plan-usage--warn {
+  color: #e6b800;
+  border-color: rgba(230, 184, 0, 0.4);
+}
+.header-plan-usage--crit {
+  color: var(--danger, #ff5c5c);
+  border-color: rgba(255, 92, 92, 0.5);
+}
+/* Marker class must out-specify the display:inline-flex !important above. */
+.header-plan-usage.header-plan-usage--hidden {
+  display: none !important;
+}
+
 .response-viewer {
   display: none;
   position: fixed;