fix(bin): register freshly spawned pi workers as Herdr agents

[witt3rd]

Intent

Everything of this Firstmate fleet now runs on the Herdr backend (the captain moved it off tmux on 2026-09-29). Freshly spawned pi worker panes are not registered with Herdr as agents: herdr pane list shows no agent and agent_status "unknown" for them, while relaunched pi panes and the primary pi pane register as "pi". Seen on 4 of 6 new Herdr workers in the Spire caretaker's home and on the animus kunchenguid#9 worker. Consequence: fm-send reports the live worker as exited and rings no doorbell, so steers sit unread until someone types into the pane by hand, and watcher liveness/stale checks may misread these panes. The Herdr pi integration is installed and current (v9) at ~/.pi/agent/extensions/herdr-agent-state.ts. Make freshly spawned pi workers on Herdr register as agents so steering and monitoring work.

#3 doesn't pass CI!
(That PR is this branch's PR. Its fork CI checks "Behavior portable serial 2" and "Behavior portable serial 4" fail in tests/fm-calm-pi-extension.test.sh and tests/fm-pi-branch-extension.test.sh because CI installs the latest public Pi, 0.99.1, while the fleet runs Pi 0.87.1 and main last passed on 0.87.1. The PR must be green before it is merged.)

What Changed

• On Herdr, fm-spawn.sh now types a launch line from the new fm_backend_herdr_launch_line in bin/backends/herdr.sh. The line sources the staged launch file inside a job-controlled /bin/sh -c 'set -m; ...', so the agent gets its own process group and takes the terminal foreground. Herdr then registers the pane as an agent, and fm-send and the watchers see the worker as live. Other backends keep the . '<file>' line.
• Adds a launch-line unit test and a live e2e test for pi launch registration, registers both in fm-test-run.sh, updates the existing Herdr remote tests and fixture for the new launch line, and documents the behavior in docs/herdr-backend.md, docs/configuration.md and docs/verification/runtime-backends.md.
• Unrelated to the Herdr fix (separate commit 7491318, CI only): in .github/workflows/ci.yml, both jobs that install Pi now pin @earendil-works/pi-coding-agent@0.87.1. Unpinned CI installed Pi 0.99.1, which broke fm-calm-pi-extension and fm-pi-branch-extension in the portable serial shards.

Risk Assessment

✅ Low: On Herdr, the typed launch line now sources the staged launch file inside a job-controlled /bin/sh, and this is applied only to that backend. It is quoted correctly and covered by pty and live tests. CI pins Pi to 0.87.1, which addresses the stated CI failures. The one behavior change is that launch commands now run under POSIX sh on Herdr, and the change documents this.

Testing

I ran the launch-line unit test and the live end-to-end test against real Herdr 0.9.2 and Pi 0.87.1. In the live test, a Pi started through the new launch line registered as "pi" even when the pane shell had no job control. The counterfactual, a plain sourced launch, stayed unregistered with the shell in the foreground group. Both tests passed. The process-group scenario was covered only by the unit test, which is not live. The CI Pi-version pinning was not driven live, because it only takes effect on GitHub Actions.

• Live validation: ✅ go - 2 of 4 scenarios driven live against the product

Scenario	Result	Live	Evidence
Fresh pi worker launched via the Herdr launch line registers as agent 'pi' under real Herdr, with no job control in the pane shell	✅ pass	live	tests/fm-herdr-pi-launch-registration-live-e2e.test.sh; run.log
Adversarial: the old sourced launch shape stays unregistered under Herdr (counterfactual), so the launch line is what fixes it	✅ pass	live	live e2e counterfactual output in run.log: foreground bash plus pi
Launch line puts the agent in its own foreground process group and the terminal returns to the shell afterward	⏸️ untested	no	The prior payload only ran tests/fm-backend-herdr-launch-line.test.sh, which uses real shell processes but not the live Herdr product, so it did not establish a live result for this scenario.
CI on Pi 0.99.1 goes green (the two extension tests that were failing)	⏸️ untested	no	Only Pi 0.87.1 is installed locally, and I could not install 0.99.1 system-wide. The result depends on GitHub Actions running the workflow change in .github/workflows/ci.yml.

Evidence: test run transcript

Source: test run transcript

== tests/fm-backend-herdr-launch-line.test.sh
ok - herdr launch line: from a shell without job control, the agent runs as its own foreground process group and the terminal returns to the shell
ok - herdr launch line counterfactual: a plain '. <file>' agent shares the pane shell's group, the shape Herdr never registers
rc=0
== tests/fm-herdr-pi-launch-registration-live-e2e.test.sh
# pi 0.87.1 under herdr 0.9.2: launch-line pane registered pi, foreground [{"name":"pi","argv0":null}]
ok - real herdr 0.9.2 + pi 0.87.1: a Pi started through the Herdr launch line registers as an agent even when the pane shell has no job control
# herdr 0.9.2 still leaves a sourced, continuously redrawing Pi unregistered under a shell without job control (foreground [{"name":"bash","argv0":null},{"name":"pi","argv0":null}]): the launch line is what registers it
rc=0

Pipeline

Updates from git push no-mistakes

✅ **intent** - passed

✅ No issues found.

✅ **Rebase** - passed

✅ No issues found.

✅ **Review** - passed

✅ No issues found.

✅ **Test** - passed

✅ No issues found.

• Live validation: ✅ go - 2 of 4 scenarios driven live against the product

Scenario	Result	Live	Evidence
Fresh pi worker launched via the Herdr launch line registers as agent 'pi' under real Herdr, with no job control in the pane shell	✅ pass	live	tests/fm-herdr-pi-launch-registration-live-e2e.test.sh; run.log
Adversarial: the old sourced launch shape stays unregistered under Herdr (counterfactual), so the launch line is what fixes it	✅ pass	live	live e2e counterfactual output in run.log: foreground bash plus pi
Launch line puts the agent in its own foreground process group and the terminal returns to the shell afterward	⏸️ untested	no	The prior payload only ran tests/fm-backend-herdr-launch-line.test.sh, which uses real shell processes but not the live Herdr product, so it did not establish a live result for this scenario.
CI on Pi 0.99.1 goes green (the two extension tests that were failing)	⏸️ untested	no	Only Pi 0.87.1 is installed locally, and I could not install 0.99.1 system-wide. The result depends on GitHub Actions running the workflow change in .github/workflows/ci.yml.

• bash tests/fm-backend-herdr-launch-line.test.sh
• bash tests/fm-herdr-pi-launch-registration-live-e2e.test.sh (real herdr 0.9.2 and pi 0.87.1, in a lab session)

✅ **Document** - passed

✅ No issues found.

⚠️ **Lint** - 1 warning

• ⚠️ linter found issues (exit code 1)

✅ **Push** - passed

✅ No issues found.