docs: add Windows setup section (Git Bash/WSL prereqs) — ROADMAP #51

Users were hitting:
- bash: cargo: command not found (Rust not installed or not on PATH)
- C:\... vs /c/... path confusion in Git Bash
- MINGW64 prompt misread as broken install

New '### Windows setup' section in README covers:
1. Install Rust via rustup.rs
2. Open Git Bash (MINGW64 is normal)
3. Verify cargo --version / run . ~/.cargo/env if missing
4. Use /c/Users/... paths
5. Clone + build + run steps

WSL2 tip added for lower-friction alternative.

ROADMAP #51 filed.

ROADMAP.md

@@ -526,3 +526,5 @@ Model name prefix now wins unconditionally over env-var presence. Regression tes
 49. **Resumed slash command errors emitted as prose in `--output-format json` mode** — dogfooded 2026-04-09. `claw --output-format json --resume <session> /commit` called `eprintln!()` and `exit(2)` directly, bypassing the JSON formatter. Both the slash-command parse-error path and the `run_resume_command` Err path now check `output_format` and emit `{"type":"error","error":"...","command":"..."}`. **Done at `da42421` 2026-04-09**. Source: gaebal-gajae ROADMAP #26 track; Jobdori dogfood.
 
 50. **PowerShell tool is registered as `danger-full-access` — workspace-aware reads still require escalation** — dogfooded 2026-04-10. User running `workspace-write` session mode (tanishq_devil in #claw-code) had to use `danger-full-access` even for simple in-workspace reads via PowerShell (e.g. `Get-Content`). Root cause traced by gaebal-gajae: `PowerShell` tool spec is registered with `required_permission: PermissionMode::DangerFullAccess` (same as the `bash` tool in `mvp_tool_specs`), not with per-command workspace-awareness. Bash shell and PowerShell execute arbitrary commands, so blanket promotion to `danger-full-access` is conservative — but it over-escalates read-only in-workspace operations. Fix shape: (a) add command-level heuristic analysis to the PowerShell executor (read-only commands like `Get-Content`, `Get-ChildItem`, `Test-Path` that target paths inside CWD → `WorkspaceWrite` required; everything else → `DangerFullAccess`); (b) mirror the same workspace-path check that the bash executor uses; (c) add tests covering the permission boundary for PowerShell read vs write vs network commands. Note: the `bash` tool in `mvp_tool_specs` is also `DangerFullAccess` and has the same gap — both should be fixed together. Source: tanishq_devil in #claw-code 2026-04-10; root cause identified by gaebal-gajae.
+
+51. **Windows first-run onboarding missing: no explicit Rust + shell prerequisite branch** — dogfooded 2026-04-10 via #claw-code. User hit `bash: cargo: command not found`, `C:\...` vs `/c/...` path confusion in Git Bash, and misread `MINGW64` prompt as a broken MinGW install rather than normal Git Bash. Root cause: README/docs have no Windows-specific install path that says (1) install Rust first via rustup, (2) open Git Bash or WSL (not PowerShell or cmd), (3) use `/c/Users/...` style paths in bash, (4) then `cargo install claw-code`. Users can reach chat mode confusion before realizing claw was never installed. Fix shape: add a **Windows setup** section to README.md (or INSTALL.md) with explicit prerequisite steps, Git Bash vs WSL guidance, and a note that `MINGW64` in the prompt is expected and normal. Source: tanishq_devil in #claw-code 2026-04-10; traced by gaebal-gajae.