fix(lint): ST1021 — lead JitteredTicker docstring with the type name

CI run #25838658130 against the Phase 6 commit (8191b1ee) failed
the golangci-lint step:

  internal/scheduler/jitter.go:11:1: ST1021: comment on exported
  type JitteredTicker should be of the form "JitteredTicker ..."
  (with optional leading article) (staticcheck)

The Phase 6 SCALE-M5 commit led the doc block with the Phase 6
backstory ("Phase 6 SCALE-M5 closure (2026-05-14): bounded-jitter
wrapper ...") rather than the type name. Pre-commit verification
ran `go test` + `go vet` but not staticcheck — same gap CLAUDE.md
already calls out in the "make verify" rule. The lint set in
.golangci.yml enables `staticcheck` with `checks: ["all", ...]`
which includes ST1021; the project's `gofmt + go vet + go test`
trio does NOT include it.

Restructured the comment so the first line leads with
`JitteredTicker is ...` (godoc-canonical form) and demoted the
Phase 6 backstory to a trailing paragraph. Same content, same
SLO-preservation explanation, same pre-Phase-6 contrast — just
reordered so godoc renders the documentation correctly and
staticcheck stays clean.

The local-staticcheck-binding-rule from the lockfile-regen and
fail-closed-pairing hotfixes applies here too: any future commit
that introduces an exported Go symbol must include the symbol
name in the first word of its doc block. Adding this to the
"pre-commit pattern lessons" list in the audit's Tasks-Deferred
table along with the Phase 7 update.

Verification:
  staticcheck -checks all,-<project-exclusions> \
    ./internal/scheduler/... → clean
  go test ./internal/scheduler/... -count=1 → ok (9.6s)
  gofmt -l internal/scheduler/jitter.go → clean

Closes: CI run 25838658130 lint failure on master@8191b1ee

internal/scheduler/jitter.go

@@ -8,28 +8,26 @@ import (
 	"time"
 )
 
-// Phase 6 SCALE-M5 closure (2026-05-14): bounded-jitter wrapper
-// around time.Timer to spread scheduler-loop tick co-fires.
+// JitteredTicker is a bounded-jitter wrapper around time.Timer that
+// fires on C once per interval ± jitterPct, with the jitter drawn
+// fresh on every tick. The base interval is the same as a bare
+// time.NewTicker; only the per-tick envelope changes. This preserves
+// every loop's expected SLO (a renewal scan still runs ~once per
+// hour) while breaking up the co-fire pattern that bare tickers
+// produce when multiple loops share a nominal cadence.
 //
-// Pre-Phase-6 the 15 scheduler loops in scheduler.go each used a
-// bare time.NewTicker(interval). When multiple loops share a
-// nominal cadence (e.g. several loops on a 1h interval), they
-// co-fire at the same wall-clock boundary post-server-start,
-// producing visible CPU + DB spikes at every hour boundary. The
-// renewal scan + the agent health check + the digest preview all
-// firing within milliseconds of each other on a freshly-booted
-// server can saturate the connection pool until they complete.
+// Stop must be called by the caller (typically via defer) to release
+// the goroutine. After Stop, the C channel is closed.
 //
-// JitteredTicker replaces the bare time.NewTicker with a goroutine
-// that fires C once per interval ± jitterPct, drawn fresh on every
-// tick. The base interval is the same as before; only the per-tick
-// envelope changes. This preserves every loop's expected SLO (a
-// renewal scan still runs ~once per hour) while breaking up the
-// co-fire pattern.
-//
-// JitteredTicker.Stop() must be called by the caller (typically via
-// defer) to release the goroutine. After Stop, the C channel is
-// closed.
+// Phase 6 SCALE-M5 (2026-05-14) introduced this wrapper. Pre-Phase-6
+// the 15 scheduler loops in scheduler.go each used a bare
+// time.NewTicker(interval); when multiple loops shared a nominal
+// cadence (e.g. several loops on a 1h interval), they co-fired at
+// the same wall-clock boundary post-server-start, producing visible
+// CPU + DB spikes at every hour boundary. The renewal scan + the
+// agent health check + the digest preview all firing within
+// milliseconds of each other on a freshly-booted server could
+// saturate the connection pool until they completed.
 type JitteredTicker struct {
 	// C is the channel a tick fires on. Read this in the loop's
 	// select{} the same way you'd read time.Ticker.C.