docs(readme): document cloning a GitHub repo into a case

The Clone Repo tab shipped in 1.16.2 (#236) but only ever appeared in
docs/architecture-invariants.md, so nothing a user reads first mentioned
that a repository URL is a way to start a case. Adds it to More Features
and to the working-directory row of the create-a-session table, where the
question "how do I get a project in here" actually gets asked.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -252,7 +252,7 @@ Click **+ New Session** (or **Quick Start**). A session is one AI CLI running in
 
 | Field                        | What it does                                                                                                        |
 | ---------------------------- | ------------------------------------------------------------------------------------------------------------------- |
-| **Working directory / case** | The folder the agent operates in. A "case" is just a named working dir Codeman remembers.                           |
+| **Working directory / case** | The folder the agent operates in. A "case" is just a named working dir Codeman remembers. **Add Case** creates one from scratch, links an existing folder, or clones a GitHub repo straight into one (**Clone Repo**). |
 | **CLI / run mode**           | `Claude` (default), `OpenCode`, `Codex`, `Antigravity`, `Gemini`, or `Terminal` (plain shell).                       |
 | **Model**                    | Per-session model (App Settings → Claude Model). A soft default — `/model` still works in-session.                  |
 | **Effort / Ultracode**       | Reasoning effort (`low`–`max`) or `ultracode` for dynamic multi-agent workflows. Switchable anytime with `/effort`. |
@@ -428,6 +428,7 @@ PTY Output → 16ms Server Batch → DEC 2026 Wrap → SSE → Client rAF → xt
 
 - **Background daemon & service install** — `codeman web -d` runs the server detached with a pidfile, `~/.codeman/web.log`, and verified startup (it polls the server until it answers, so a port clash never reads as success); `codeman service install` writes a systemd user unit (Linux) or LaunchAgent (macOS) with your shell's PATH baked in, so an nvm or Homebrew `node`, `tmux` and `claude` are actually found. Secrets are never written into unit files
 - **Self-update** — git-clone installs under systemd/launchd update in place from **App Settings → Updates**: it detects the latest release, auto-stashes a dirty tree, and streams build progress across the service restart (npm installs report as non-updatable)
+- **Clone a GitHub repo as a case** — paste a repository URL into **Add Case → Clone Repo** and Codeman clones it into `~/codeman-cases/<name>` and registers it as a normal case, ready to run an agent in. It preflights the URL while you type (tells you whether it can be cloned anonymously and offers the repo's real branches and tags for the optional branch/tag field), fills the case name in from the URL, and lets you pick which CLI the Run button should use. Public repositories over `https://`; Codeman never collects or stores credentials
 - **Multi-CLI** — run **Claude Code**, **OpenCode**, **Codex**, **Antigravity**, or **Gemini** per session; env-var prefixes auto-gate (`CLAUDE_CODE_*` vs `OPENCODE_*` vs `CODEX_*` vs `ANTIGRAVITY_*` vs `GEMINI_*`/`GOOGLE_*`). See [`docs/opencode-integration.md`](docs/opencode-integration.md)
 - **Docker sessions** — run a case inside an isolated, hardened container. One checkbox on **Create New** spins up a container with sensible defaults and starts the agent inside it; multiple sessions share one per-case container; export a container + its workspace to a portable `.tar.gz` to move it to another machine. See [`docs/docker-cases.md`](docs/docker-cases.md)
 - **Remote SSH sessions** — point a case at another machine and run the agent there inside a durable remote tmux: survives SSH drops, auto-reconnects, and can discover + attach sessions already running on the host. See [`docs/remote-sessions.md`](docs/remote-sessions.md)