homelab: v0.6.0 — usage telemetry (usage top), evidence-driven verb prioritization

Answers the question that drove the whole CLI — which verbs to add next — with
data instead of one maintainer's habits, and resolves the cross-user-usage ask
in-bounds (no reading anyone's home).

- emit on dispatch: every verb fire-and-forgets one Loki line {job,user,verb} +
  "exit=N ver=X". ONLY the verb path + exit code — never args, paths, flags, or
  secrets (the emit never sees arguments). Best-effort: 800ms timeout, errors
  swallowed, never affects the command; opt-out HOMELAB_TELEMETRY=0. Discovery
  verbs (manifest/version/help) and usage itself don't self-record.
- usage top [--since 30d] [--user U] [--json]: ranks verbs via
  sum by (verb)(count_over_time({job="homelab-usage"}[…])) against the shared
  Loki. Cross-user analytics WITHOUT touching ~/.claude — the privacy-preserving
  answer to "what does the team use".
- Loki sink (zero new infra, dogfoods v0.5 logs path); push verified HTTP 204 no
  auth. ADR docs/adr/0011.

Live-verified: ran 4 verbs, usage top ranked them correctly (metrics query=2).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cli/telemetry.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// usageJob is the Loki stream job label for homelab usage telemetry.
+const usageJob = "homelab-usage"
+
+// emitUsage best-effort records one verb invocation to Loki for cross-user
+// usage analytics. Labels are low-cardinality (job/user/verb); the line carries
+// only exit code + CLI version. NEVER args, paths, flags, or secrets. It must
+// never affect the command: all errors are swallowed and a tight timeout bounds
+// the cost. Opt out with HOMELAB_TELEMETRY=0.
+func emitUsage(verb string, runErr error) {
+	switch os.Getenv("HOMELAB_TELEMETRY") {
+	case "0", "off", "false", "no":
+		return
+	}
+	if verb == "" || strings.HasPrefix(verb, "usage") {
+		return // don't self-record the analytics reader
+	}
+	exit := 0
+	if runErr != nil {
+		exit = 1
+	}
+	body, err := json.Marshal(lokiPush{Streams: []lokiStream{{
+		Stream: map[string]string{"job": usageJob, "user": currentUser(), "verb": verb},
+		Values: [][2]string{{
+			strconv.FormatInt(time.Now().UnixNano(), 10),
+			"exit=" + strconv.Itoa(exit) + " ver=" + version,
+		}},
+	}}})
+	if err != nil {
+		return
+	}
+	req, err := http.NewRequest("POST", "https://"+lokiHost+"/loki/api/v1/push", bytes.NewReader(body))
+	if err != nil {
+		return
+	}
+	req.Header.Set("Content-Type", "application/json")
+	resp, err := clientDialingIP(internalLBIP, 800*time.Millisecond).Do(req)
+	if err != nil {
+		return
+	}
+	resp.Body.Close()
+}
+
+type lokiPush struct {
+	Streams []lokiStream `json:"streams"`
+}
+
+type lokiStream struct {
+	Stream map[string]string `json:"stream"`
+	Values [][2]string       `json:"values"`
+}