fix(install.ps1): remove UTF-8 BOM that breaks irm | iex path

[LifeJiggy]

Title: fix(install.ps1): remove UTF-8 BOM that breaks irm | iex path

What does this PR do?

The UTF-8 BOM (EF BB BF) at byte 0 of scripts/install.ps1 causes [scriptblock]::Create to fail with 'The assignment expression is not valid' on param defaults, breaking the canonical irm https://... | iex one-liner for Windows installation.

PowerShell's normal file-execution path (& .\install.ps1) handles BOMs fine, but the irm-and-iex path uses [scriptblock]::Create((irm ...)) which does NOT strip BOMs — the BOM lands inside the param() block and corrupts the parser state. Since the file contains no non-ASCII characters, the BOM is unnecessary for PS 5.1 parsing.

Related Issue

Fixes #28071

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• scripts/install.ps1: Removed the 3-byte UTF-8 BOM prefix (byte 0xEF 0xBB 0xBF)

How to Test

1. Open a fresh PowerShell 5.1 session
2. Run: irm https://raw.githubusercontent.com/LifeJiggy/hermes-agent/fix/install-ps1-bom/scripts/install.ps1 | iex
3. Verify the installer starts normally instead of failing with The assignment expression is not valid
4. Also verify & .\scripts\install.ps1 still works for local execution

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature
• I've run pytest tests/ -q and all tests pass
• I've tested on my platform: Windows 11

Documentation & Housekeeping

• N/A — no config, docs, or schema changes

[alt-glitch]

Duplicate — #28169 (merged 2026-05-19) already stripped the BOM from install.ps1 and added -Commit/-Tag pin params. This PR's change is already in main.