feat(spawn): add Treehouse worktree setup hook

[michael-sb]

Intent

Add per-project worktree setup via treehouse post_create hook. A single global hook script (bin/fm-treehouse-post-create.sh) is wired in ~/.config/treehouse/config.toml and fires when treehouse provisions or resets a worktree. It locates firstmate's data/ from its own location and runs data/-setup.sh if it exists. Non-fatal on failure, logs to state/treehouse-setup-.log. Replaces earlier fm-spawn-based approach with treehouse-native lifecycle hook.

What Changed

• Adds a Treehouse post_create hook script that runs optional per-project setup scripts from firstmate data and records non-fatal setup output under state logs.
• Extends bootstrap to detect, validate, and install the global Treehouse hook configuration with hardened command parsing and quoting.
• Updates spawn behavior, documentation, and tests for Treehouse-native worktree setup and hook environment handling.

Risk Assessment

✅ Low: Captain, the change is bounded to Treehouse hook wiring/spawn context plus focused tests, and I did not find substantiated merge-blocking or follow-up issues.

Testing

Inspected the targeted diff, ran the focused hook/bootstrap/spawn shell tests, captured reviewer-visible CLI evidence for hook wiring and setup execution/logging, and confirmed the worktree remained clean.

Evidence: treehouse-post-create-e2e-transcript

Treehouse post_create hook e2e verification
repo=/Users/michael/.no-mistakes/worktrees/458d9fed4d70/01KVSZTTNA0BR1Y3D5XK12THFM
commit=539e5297f842a684de95513470b186397e030a5a

$ FM_HOME=/var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/fm-home XDG_CONFIG_HOME=/var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/fm-home/xdg bin/fm-bootstrap.sh install treehouse-post-create-hook
installing treehouse-post-create-hook: /Users/michael/.no-mistakes/worktrees/458d9fed4d70/01KVSZTTNA0BR1Y3D5XK12THFM/bin/fm-bootstrap.sh install treehouse-post-create-hook

$ sed -n 1,20p /var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/fm-home/xdg/treehouse/config.toml
[hooks]
post_create = ["'/Users/michael/.no-mistakes/worktrees/458d9fed4d70/01KVSZTTNA0BR1Y3D5XK12THFM/bin/fm-treehouse-post-create.sh'"]

$ (cd /var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/worktrees/app && FM_HOME=/var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/fm-home /Users/michael/.no-mistakes/worktrees/458d9fed4d70/01KVSZTTNA0BR1Y3D5XK12THFM/bin/fm-treehouse-post-create.sh)

$ cat /var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/worktrees/app/setup-marker.txt
READY_FROM_SETUP

$ cat /var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/fm-home/state/treehouse-setup-app.log
setup ran in /var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/worktrees/app

$ test -f /var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/fm-home/state/treehouse-setup-app.log && test "$(cat /var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e/worktrees/app/setup-marker.txt)" = READY_FROM_SETUP
verified: bootstrap wrote the hook config, the hook selected data/app-setup.sh for the matching project worktree, setup output was logged, and the worktree was modified by setup.

Pipeline

Updates from git push no-mistakes

✅ **intent** - passed

✅ No issues found.

✅ **Rebase** - passed

✅ No issues found.

🔧 **Review** - 1 issue found → auto-fixed ✅

• ⚠️ bin/fm-bootstrap.sh:130 - treehouse_hook_command_usable accepts an executable hook path anywhere in the shell command, so a post_create entry like echo /abs/bin/fm-treehouse-post-create.sh is treated as configured even though Treehouse would never execute the hook. Bootstrap would then stay silent while per-project setup never runs; restrict the match to the executable command word, allowing only known-safe prefixes such as environment assignments.

🔧 Fix: Captain, tighten treehouse hook detection
✅ Re-checked - no issues remain.

✅ **Test** - passed

✅ No issues found.

• git status --short --branch
• git diff --stat 2a2fe0566e63b883ec53dc3e34dc14306689f989..539e5297f842a684de95513470b186397e030a5a
• git diff --name-only 2a2fe0566e63b883ec53dc3e34dc14306689f989..539e5297f842a684de95513470b186397e030a5a
• tests/fm-treehouse-post-create.test.sh
• tests/fm-bootstrap.test.sh
• tests/fm-spawn-treehouse-env.test.sh
• Created an isolated firstmate home and git worktree under /var/folders/t0/dws_m6l52lj97dkt9f4hd_sh0000gn/T/no-mistakes-evidence/01KVSZTTNA0BR1Y3D5XK12THFM/treehouse-post-create-e2e, ran bin/fm-bootstrap.sh install treehouse-post-create-hook with local FM_HOME/XDG_CONFIG_HOME, then invoked bin/fm-treehouse-post-create.sh from the matching worktree and verified the setup marker plus state/treehouse-setup-app.log.
• git status --short

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.

[michael-sb]

Sorry - my firstmate got a bit carried away - he can be quite proactive :D