fix(cli): report command errors instead of exiting silently

[Athul Nambiar (athul-22)]

Summary

browseros-cli exited with code 1 and no output at all on every command-line error — unknown flag, unknown shorthand, unknown subcommand, or any error returned from a RunE handler. A typo was indistinguishable from a crash or an unreachable server.

Fixes #2429.

Root cause

rootCmd set SilenceErrors: true, which tells Cobra not to print errors, but Execute() discarded the returned error rather than printing it itself:

err := rootCmd.Execute()
...
if err != nil {
    os.Exit(1)   // err is never printed
}

SilenceErrors is only safe when the caller reports the error. Nothing here did.

Fix

Drop SilenceErrors so Cobra reports the failure. Its default ErrPrefix() is already Error:, which matches the format output.Error already uses for in-command failures, so the two paths now read identically:

$ browseros-cli snapshot            # in-command error (unchanged)
Error: page id is required: pass -p/--page <id> ...

$ browseros-cli tabs --bogus        # Cobra-level error (was silent)
Error: unknown flag: --bogus

SilenceUsage: true is kept, so errors stay one line and don't dump the full usage block. Exit code 1 is unchanged.

Before / after

Command	Before	After
tabs --bogus	exit 1, 0 bytes out	Error: unknown flag: --bogus
snapshot -Z	exit 1, 0 bytes out	Error: unknown shorthand flag: 'Z' in -Z
definitely-not-a-command	exit 1, 0 bytes out	Error: unknown command "definitely-not-a-command" for "browseros-cli"

This also surfaces the wrapped errors config returns from its RunE (loading config: %w, saving config: %w), which were swallowed the same way.

Tests

Added TestCommandErrorsAreReportedToStderr — a table test over unknown flag / unknown shorthand / unknown command that asserts the message reaches stderr and keeps the Error: prefix. Confirmed it is a real regression test: with SilenceErrors restored it fails on all three cases with failed silently; the error must reach stderr, and passes with the fix.

Verified locally from packages/browseros-agent/apps/cli:

gofmt -l .   # clean
go vet ./... # clean
go build ./...
go test ./...
ok  browseros-cli
ok  browseros-cli/analytics
ok  browseros-cli/cmd
ok  browseros-cli/cmd/raw
ok  browseros-cli/mcp
ok  browseros-cli/update

Note

While reproducing this I noticed snapshot registers no flags, yet the agent guide shipped as browseros-cli --llm-txt documents snapshot -i five times (cmd/llm_txt.md lines 34, 36, 51, 61, 152) along with -c and -d N. The MCP snapshot tool does accept mode and depth, so the flags appear simply unwired. That is out of scope here and I'll file it separately.

[greptile-apps]

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