Rename the Go module to sneak.berlin/go/secret (closes #43)

REPO_POLICIES.md requires the module root sneak.berlin/go/<name>.
go.mod, every import (rewritten with gofmt -r), the -X flags in
script/build and the examples in the pkg READMEs now use the new path.
go mod tidy lists go-humanize and fatih/color as direct requirements,
since internal/cli imports them.

This breaks anyone who fetched or imported git.eeqj.de/sneak/secret:
they must switch to sneak.berlin/go/secret, which resolves to this
repository.

Model: opus-5-5

TODO.md

@@ -18,6 +18,14 @@ https://git.eeqj.de/sneak/secret/milestone/12
 
 # Completed Steps
 
+- 2026-10-05: The Go module path is `sneak.berlin/go/secret`, as
+  `REPO_POLICIES.md` requires, not `git.eeqj.de/sneak/secret`
+  (https://git.eeqj.de/sneak/secret/issues/43). Every import uses it, as do the
+  `-X` flags in `script/build` that stamp the version and commit shown by
+  `secret info`, and the examples in `pkg/agehd/README.md` and
+  `pkg/bip85/README.md`. `go mod tidy` now lists `github.com/dustin/go-humanize`
+  and `github.com/fatih/color`, which `internal/cli` imports, as direct
+  requirements. Code that imported the old path must switch to the new one.
 - 2026-10-04: `make fmt` formats every markdown file with prettier (4-space
   tabs, `proseWrap: always`) as well as the Go code, and `make fmt-check` checks
   both, as the model scripts in the `prompts` repo do