Adds RODNEY_HOME environment variable to customize the state directory, instead of it being hardcoded to ~/.rodney.

This is a potential solution for #6 that could support per-project, or temporary, state directories, while imposing no overhead/impact for users that don't need it.

I choose env variable as the mechanism because there are already some env vars that control how the binary works (ROD_CHROME_BIN, HTTPS_PROXY), and the documented CLI flags (eg. for accessibility testing) seem to be subcommand-specific.

Designed and developed using Claude Code (Opus 4.6), I personally reviewed the output and tested it locally before submitting this PR.

This is the complete plan Claude implemented:

Add RODNEY_HOME environment variable

Context

The rodney data directory (~/.rodney/) is hard-coded via the stateDir() function in main.go:41-44. There is no way to customize it, which blocks per-project or multi-session usage (see GitHub issue #6). We'll add a RODNEY_HOME env var to allow overriding the directory.

Changes

1. rodney-src/main.go (lines 41-44)

Replace the current stateDir() with a minimal version that checks RODNEY_HOME first:

func stateDir() string {
    if dir := os.Getenv("RODNEY_HOME"); dir != "" {
        return dir
    }
    home, _ := os.UserHomeDir()
    return filepath.Join(home, ".rodney")
}

No validation or directory creation here — saveState() (line 63) and cmdStart() (line 262-263) already call os.MkdirAll on the returned path.

2. rodney-src/main_test.go

Add tests (no browser needed — pure function tests):

• TestStateDir_Default — unset RODNEY_HOME, verify stateDir() returns $HOME/.rodney
• TestStateDir_EnvVar — set RODNEY_HOME to a temp dir, verify stateDir() returns it

3. rodney-src/help.txt

Add RODNEY_HOME to the configuration/environment section.

4. rodney-src/README.md

Add RODNEY_HOME to the configuration table.

Verification

1. Run tests: cd rodney-src && go test -run TestStateDir -v
2. Build: go build -o rodney .
3. Manual smoke test: RODNEY_HOME=/tmp/rodney-test ./rodney start && ls /tmp/rodney-test/ && RODNEY_HOME=/tmp/rodney-test ./rodney stop