Windows: an npm-installed OMP pane is never detected; agent start --kind omp times out

Is this a reproducible bug?

• I confirm this is a reproducible bug, not a feature request, idea, question, contribution proposal, or direction check.
• I reproduced this bug on the version and environment reported below using the exact steps provided.

Current behavior

On Windows, an OMP pane never registers with Herdr. The OMP TUI runs fine in the pane, the official integration is installed, but the pane stays agent_status: "unknown", herdr agent list stays empty, and herdr agent start --kind omp times out.

With OMP ready in pane w5:p1 (title π > ..., status bar rendered):

$ herdr pane get w5:p1
{"result":{"pane":{"agent_status":"unknown", ... , "terminal_title":"π > Review PR 231 CI status"}}}

$ herdr agent list
{"result":{"agents":[]}}

$ herdr agent start omp-test --kind omp --pane w5:p1 --timeout 90000
{"error":{"code":"timeout","message":"timed out waiting for agent startup"}}

Two related observations on the same pane: herdr pane process-info lists only the pane shell (pwsh.exe) and no OMP child process, and a hand-sent pane.report_agent for that pane with source: "herdr:omp" / agent: "omp" answers {"result":{"type":"ok"}} without anything registering.

Control on the same machine and the same Herdr session: running codex in a pane registers immediately ("agent":"codex","agent_status":"idle"), so this is specific to OMP panes.

Expected behavior

An OMP pane should register as an agent: it should appear in herdr agent list with an idle/working/blocked state, herdr agent start --kind omp should succeed, and the installed OMP integration (herdr integration status reports omp: current (v10)) should provide its state and session identity.

Reproduction

1. Windows 11 Pro (10.0.26200), Herdr 0.9.1 stable, server started from a Windows OpenSSH session, PowerShell 7.6.6 pane shell. OMP installed globally with npm: npm i -g @oh-my-pi/pi-coding-agent (omp 18.2.4, reproduced on 18.2.0 as well), bun 1.4.2. The omp shim is %APPDATA%\npm\omp.cmd; while running, OMP's process is bun.exe ...\node_modules\@oh-my-pi\pi-coding-agent\dist\cli.js.
2. herdr integration install omp → installed omp integration to C:\Users\<user>\.omp\agent\extensions\herdr-omp-agent-state.ts; herdr integration status → omp: current (v10).
3. herdr pane split --current --direction down --cwd "C:\source\sebscribe-desktop" --no-focus, then herdr pane run <pane> "omp".
4. Wait until the OMP TUI is interactive, then run herdr pane get <pane>, herdr agent list and herdr agent start test --kind omp --pane <pane> --timeout 90000. Results are the three outputs in "Current behavior".
5. Control pane: herdr pane run <other-pane> "codex" → that pane registers as codex / idle within a few seconds.

Impact

On Windows I can only drive OMP panes at the terminal level (pane read / pane run). Agent-level control — agent prompt, agent wait, blocked/idle detection, notifications and sidebar rollups — is unavailable for OMP even though the integration is installed and reporting, while the same machine handles codex normally. OMP is my main agent, so Herdr's agent features are effectively unavailable for it on this host.

Environment

• Herdr version: 0.9.1 (client and server; same behavior with a 0.9.0 server and 0.9.1 client)
• Update channel (stable or preview): stable
• Operating system: Windows 11 Pro, 10.0.26200, x64
• Terminal: Windows Terminal (Herdr server started from a Windows OpenSSH session; panes run PowerShell 7.6.6)
• Shell, if relevant: PowerShell 7.6.6 (pwsh.exe) pane shell
• Relevant config, if any: default config.toml; OMP 18.2.4 installed via npm global (@oh-my-pi/pi-coding-agent); Herdr OMP integration v10