Claude/windows install compatibility tr di s (#3)

* Fix Windows PowerShell 5.1 compatibility in installer

Use $env:PROCESSOR_ARCHITECTURE for arch detection instead of
RuntimeInformation::OSArchitecture which may not be loaded in
every Windows PowerShell 5.1 session. Also fix null-reference
when user PATH environment variable is empty.

https://claude.ai/code/session_01VFiRDM2ZweyacXN5JneVoP

* Fix executable resolution and tar extraction on Windows

resolveExecutable() used `sh -lc "command -v ..."` which doesn't work
on Windows (no sh). Now uses `cmd /c where` on win32. Also make tar
workspace restoration tolerate symlink failures on Windows — .bin/
symlinks can't be created without Developer Mode, but the actual
package directories are extracted fine.

https://claude.ai/code/session_01VFiRDM2ZweyacXN5JneVoP

* Broad Windows compatibility fixes across the codebase

- runtime.ts: Use path.delimiter instead of hardcoded ":" for PATH
  construction — was completely broken on Windows
- executables.ts: Add Windows fallback paths for Chrome, Edge, Brave,
  and Pandoc in Program Files; skip macOS-only paths on win32
- node-version.ts, check-node-version.mjs, bin/feynman.js: Show
  Windows-appropriate install instructions (irm | iex, nodejs.org)
  instead of nvm/curl on win32
- preview.ts: Support winget for pandoc auto-install on Windows, and
  apt on Linux (was macOS/brew only)
- launch.ts: Catch unsupported signal errors on Windows
- README.md: Add Windows PowerShell commands alongside macOS/Linux
  for all install instructions

https://claude.ai/code/session_01VFiRDM2ZweyacXN5JneVoP

* fix: complete windows bootstrap hardening

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Advait Paliwal <advaitspaliwal@gmail.com>

README.md

@@ -13,28 +13,52 @@
 
 ### Installation
 
+**macOS / Linux:**
+
 ```bash
 curl -fsSL https://feynman.is/install | bash
 ```
 
+**Windows (PowerShell):**
+
+```powershell
+irm https://feynman.is/install.ps1 | iex
+```
+
 If you install via `pnpm` or `bun` instead of the standalone bundle, Feynman requires Node.js `20.18.1` or newer.
 
 ### Skills Only
 
 If you want just the research skills without the full terminal app:
 
+**macOS / Linux:**
+
 ```bash
 curl -fsSL https://feynman.is/install-skills | bash
 ```
 
+**Windows (PowerShell):**
+
+```powershell
+irm https://feynman.is/install-skills.ps1 | iex
+```
+
 That installs the skill library into `~/.codex/skills/feynman`.
 
 For a repo-local install instead:
 
+**macOS / Linux:**
+
 ```bash
 curl -fsSL https://feynman.is/install-skills | bash -s -- --repo
 ```
 
+**Windows (PowerShell):**
+
+```powershell
+& ([scriptblock]::Create((irm https://feynman.is/install-skills.ps1))) -Scope Repo
+```
+
 That installs into `.agents/skills/feynman` under the current repository.
 
 ---