feat(supervision): port upstream self-update skill and ghost-text fix to herdr

[leo1oel]

What & why

Adapts the herdr-backend fork to two upstream firstmate commits that were genuinely missing after an audit of the post-fork upstream history. A straight rebase/merge of upstream/main was rejected on purpose: this fork deliberately dropped tmux + treehouse + fm-bootstrap and re-implemented those features for the herdr backend, so selective porting is the maintenance model. Base is herdr-backend (the fork's trunk), not main (which mirrors upstream).

Ported changes

kunchenguid#61 — self-update skill (/updatefirstmate)

• New bin/fm-update.sh: fast-forwards the running firstmate repo and every registered secondmate home from origin, fast-forward only, mirroring fm-fleet-sync safety (never force / merge-commit / stash; skip + report dirty / diverged / offline / wrong-branch), so prime directive chore: port upstream brief-contract and skill-set doc fixes (#73, #72) #3 holds and no unlanded work is discarded.
• herdr adaptation: upstream leases secondmate homes at a detached HEAD on the default branch (treehouse). This fork's homes are herdr worktrees on a lease branch secondmate-<id>, so ff_target accepts the default branch or that lease branch or a detached HEAD and fast-forwards it to origin/<default>. Nudges target fm-<id> (the herdr pane, resolved by fm-send) instead of tmux window targets.
• New /updatefirstmate skill, AGENTS.md §12, and README entries.
• New tests/fm-update.test.sh — 12 cases, including a herdr-specific lease-branch skip test.

kunchenguid#59 — composer detection ignores Claude ghost text

Claude renders a dim/faint predicted-next-prompt suggestion inside an otherwise-empty composer; the herdr composer detector (shared by the away-mode daemon and fm-send) would misread it as pending input. Both upstream prongs ported:

• Prong 1: launch claude with CLAUDE_CODE_ENABLE_PROMPT_SUGGESTION=false (per-launch env prefix in fm-spawn.sh, scoped to firstmate-launched agents; never touches the captain's global config).
• Prong 2: fm-herdr-lib.sh now captures herdr pane read --format ansi and strips dim/faint (SGR 2) runs via a new fm_herdr_strip_ghost (ported verbatim from upstream's hardened awk, which preserves SGR-colored normal-intensity typed text) before the existing border-aware classification. The styled capture stays internal; fm-peek and human-facing reads stay plain.
• New tests/fm-composer-ghost.test.sh — 9 cases. AGENTS.md §4/§8 synced.

Deferred (separate decision)

tasks-axi (kunchenguid#55/kunchenguid#60) intentionally not ported: tasks-axi is not installed here, upstream treats it as dormant/conditional scaffolding, and its wiring hangs off the fm-bootstrap this fork removed. Revisit if/when the tool is adopted.

Validation

• All 8 behavior suites pass (incl. the 2 new ones).
• shellcheck bin/*.sh tests/*.sh clean; bash -n clean.
• CLAUDE.md → AGENTS.md and .claude/skills symlink invariants hold.
• Live smoke: bin/fm-update.sh on a non-default branch safely skips (never forces), prints correct action lines, leaves HEAD untouched.

Note: the local no-mistakes gate is pinned to the repo default branch main (upstream mirror), so it could not validate a branch based on herdr-backend. Validation above was run by hand.

🤖 Generated with Claude Code