Allow customizing the project identifier/name

Problem

Claude Code derives the project identifier from the full absolute directory path (e.g., -Users-jaisonerick-code-jaisonerick-second-brain). This results in long, unwieldy identifiers that are hard to read and distinguish, especially when working with deeply nested directory structures or multiple projects under the same parent paths.

Proposal

Add a way to set a custom project name/identifier, either via:

1. A setting in .claude/settings.json (project-level), e.g.:

``json
{
"projectName": "second-brain"
}
``

1. A field in CLAUDE.md frontmatter
2. A CLI flag like --project-name

This would affect anywhere the project identifier is used internally (session storage paths, display, etc.).

Use Case

Users who organize code in structured directories (e.g., ~/code/<org>/<repo>) end up with project identifiers that repeat redundant path segments. A short, human-readable project name would make it easier to identify projects in session history and internal storage.