feat(diary): channels, components and config/log.yaml

- stderr and null drivers; per-component levels from log.components
- SUMMER_LOG__ overrides parse as strings and overlay the defaults key by key
- Validation names the key: driver, format, level, days, stack children and cycles, daily path outside the root
- summer new writes config/log.yaml (stack of console and daily, river warn, http info)
- docs/services/logging.md: channels, config/log.yaml, component loggers, daily files, redaction
- Log keys in the configuration docs; ExampleFor backs the docs snippet

modules/diary/example_test.go

@@ -0,0 +1,34 @@
+package diary_test
+
+import (
+	"context"
+	"log/slog"
+	"os"
+
+	"git.golem15.com/golem15/summercms/modules/diary"
+)
+
+// blogLog is the component logger of a blog plugin, created once in a
+// package var block, before diary is set up.
+var blogLog = diary.For("blog")
+
+func ExampleFor() {
+	// Before diary.Setup runs, records go to the process default logger.
+	// This one drops the time so the output is stable.
+	previous := slog.Default()
+	defer slog.SetDefault(previous)
+	slog.SetDefault(slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
+			if len(groups) == 0 && a.Key == slog.TimeKey {
+				return slog.Attr{}
+			}
+			return a
+		},
+	})))
+
+	// After diary.Setup the same record reaches the configured channels and
+	// passes log.components.blog, else log.level.
+	blogLog.InfoContext(context.Background(), "post published", "id", 7)
+	// Output:
+	// level=INFO msg="post published" component=blog id=7
+}