Set the time zone in main and run Entry in its own test process (closes #192)

cli.Entry() set time.Local to UTC and ended with memguard.Purge(), and
TestEntryWipesBuffersAndReturnsExitCode ran it in the same process as
the other tests. A timer left by an earlier test could read time.Local
as it changed, which the race detector reported on some runs, and the
purge could destroy a buffer still in use, the likeliest cause of a
crash seen on another run.

main() in cmd/secret now sets time.Local before it calls cli.Entry();
the test that runs the built binary with TZ=America/New_York still
covers it. The Entry test runs cli.Entry() in a copy of the test binary
started with SECRET_TEST_RUN_ENTRY set, which init picks up so that
TestMain does not run there.

Model: opus-5-5

TODO.md

@@ -18,6 +18,15 @@ https://git.eeqj.de/sneak/secret/milestone/12
 
 # Completed Steps
 
+- 2026-10-15: `make test` no longer fails on some runs in `internal/cli`
+  (https://git.eeqj.de/sneak/secret/issues/192). `cli.Entry()` set `time.Local`
+  to UTC and ended by wiping every memguard buffer, and a test ran it in the
+  same process as the other tests. A timer left by an earlier test could read
+  `time.Local` as it changed, which the race detector reported, and the wipe
+  could destroy a buffer still in use, the likeliest cause of a crash of the
+  test process on another run. `main()` in `cmd/secret` now sets `time.Local`
+  before it calls `cli.Entry()`, and that test runs `cli.Entry()` in a process
+  of its own.
 - 2026-10-14: A wrong passphrase, from `SB_UNLOCK_PASSPHRASE` or typed at the
   prompt, gives the error `wrong passphrase for unlocker <id>`
   (https://git.eeqj.de/sneak/secret/issues/157). It used to be age's "no