Move internal/log from apex/log to log/slog (closes #77)

internal/log now logs through log/slog. After Init, records go to a small
slog.Handler that prints the same lines as before; before Init they go to
slog.Default(). The helpers and their call sites are unchanged. With
NO_COLOR set on a terminal, log lines are no longer colored.

pterm is dropped: it only printed progress lines, which fmt now writes
directly, outside slog. apex/log, pterm and their indirect dependencies
leave go.mod; golang.org/x/term becomes direct.

simplelog is not imported: importing it replaces slog's default handler in
every program that imports package mfer. The logger stays process-global,
since injecting it would change package mfer's API.

Progress and log lines now share the logger's lock, so the check progress
test runs check ten times to catch a missing wait.

Model: opus-5-5

go.mod

@@ -3,42 +3,33 @@ module sneak.berlin/go/mfer
 go 1.23
 
 require (
-	github.com/apex/log v1.9.0
 	github.com/davecgh/go-spew v1.1.1
 	github.com/dustin/go-humanize v1.0.1
 	github.com/google/uuid v1.1.2
 	github.com/klauspost/compress v1.18.2
 	github.com/multiformats/go-multihash v0.2.3
-	github.com/pterm/pterm v0.12.35
 	github.com/spf13/afero v1.8.0
 	github.com/stretchr/testify v1.8.1
 	github.com/urfave/cli/v2 v2.27.7
+	golang.org/x/term v0.0.0-20210927222741-03fcf44c2211
 	google.golang.org/protobuf v1.28.1
 )
 
 require (
-	github.com/atomicgo/cursor v0.0.1 // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.7 // indirect
-	github.com/fatih/color v1.7.0 // indirect
-	github.com/gookit/color v1.4.2 // indirect
 	github.com/klauspost/cpuid/v2 v2.0.9 // indirect
-	github.com/mattn/go-colorable v0.1.2 // indirect
-	github.com/mattn/go-isatty v0.0.8 // indirect
-	github.com/mattn/go-runewidth v0.0.13 // indirect
+	github.com/kr/pretty v0.2.0 // indirect
 	github.com/minio/sha256-simd v1.0.0 // indirect
 	github.com/mr-tron/base58 v1.2.0 // indirect
 	github.com/multiformats/go-varint v0.0.6 // indirect
-	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/rivo/uniseg v0.2.0 // indirect
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
 	github.com/spaolacci/murmur3 v1.1.0 // indirect
-	github.com/xo/terminfo v0.0.0-20210125001918-ca9a967f8778 // indirect
 	github.com/xrash/smetrics v0.0.0-20240521201337-686a1a2994c1 // indirect
 	golang.org/x/crypto v0.0.0-20220525230936-793ad666bf5e // indirect
 	golang.org/x/sys v0.1.0 // indirect
-	golang.org/x/term v0.0.0-20210927222741-03fcf44c2211 // indirect
 	golang.org/x/text v0.3.6 // indirect
+	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 	lukechampine.com/blake3 v1.1.6 // indirect
 )