- Use PATH-resolved `bash` as first token instead of quoted `.exe` path
so Claude Code v2.1.116 argv duplication does not feed a binary to
bash as its $0 (repro: exit 126 "cannot execute binary file").
- Point the command at `observe-wrapper.sh` and pass distinct `pre` /
`post` positional arguments so PreToolUse and PostToolUse are
registered as separate entries.
- Normalize the wrapper path to forward slashes before embedding in the
hook command to avoid MSYS backslash surprises.
- Write UTF-8 (no BOM) with CRLF normalized to LF so downstream JSON
parsers never see mixed line endings.
- Preserve existing hooks (legacy `observe.sh`, third-party entries)
by appending only when the canonical command string is not already
registered. Re-runs are idempotent ([SKIP] both phases).
- Keep the script compatible with Windows PowerShell 5.1: fall back to
a manual PSCustomObject → Hashtable conversion when
`ConvertFrom-Json -AsHashtable` is unavailable, and materialize hook
arrays as `System.Collections.ArrayList` so single-element arrays
survive PS 5.1 `ConvertTo-Json` serialization.
Companion to PR #1524 (settings.local.json shape fix) and PR #1540
(install_hook_wrapper.ps1 argv-dup fix).
