feat(harness): add cursor (Cursor CLI) as a verified adapter

[cybercat-yanik]

What

Adds cursor (the Cursor CLI, binary cursor-agent) as a sixth verified harness adapter. This opens the Cursor subscription model catalog (Grok 4.5, Codex/GPT tiers, Sonnet, Gemini; enumerable via cursor-agent --list-models) as crewmate/secondmate dispatch targets, which is especially useful for captains who reach some of these models only through Cursor.

Adapter facts (all verified empirically on cursor-agent 2026.07.09-a3815c0, per CONTRIBUTING)

• Launch: cursor-agent --force --model <id> "$(cat <brief>)"; --force auto-approves execution and a crewmate ran fully unattended (file edits + shell commands).
• Busy signature: ctrl+c to stop, shown iff a turn is running. The spinner word varies (Working/Running), so the cancel hint is the signature. It is end-anchored in the busy regexes because unlike the other tokens it is generic English a transcript could contain mid-line; verified live both ways (decoy phrase mid-line reads idle, real turn reads busy).
• Exit/interrupt: /exit or /quit (slash popup, the usual too-fast-Enter hazard; fm-send's retried Enter lands it); single Ctrl+C cancels a turn.
• Detection: CURSOR_AGENT=1 env marker; ancestry matches the full binary name *cursor-agent* (a bare *cursor* would match the Cursor IDE's own processes from its integrated terminal) and is ordered before *claude* because cursor's runtime is claude-code-derived (AI_AGENT=claude-code_*, but no CLAUDECODE).
• Effort axis: none; Cursor model ids bake reasoning effort into the name (grok-4.5-xhigh). The bootstrap validator rejects an effort axis on cursor profiles like it does for opencode, and fm-spawn records but never passes it. The SKILL documents Cursor's shifted display names (id grok-4.5-xhigh displays as plain "Cursor Grok 4.5").
• Turn-end: no hook. A Claude-style .claude/settings.local.json Stop hook verifiably does not fire despite the claude-code-derived runtime, so cursor crewmates ride busy-regex stale-pane supervision; the launch template is identical for ship/scout/secondmate.
• Composer: placeholder ghost text is dim (SGR 2, verified via raw styled capture), so the generic ghost-stripper handles it with no FM_COMPOSER_IDLE_RE override; fm_tmux_composer_state and fm_pane_is_busy were exercised live against idle and mid-turn panes. One quirk recorded: an Enter in the same keystroke burst as the text can be swallowed; fm-send's settle+retry covers it.
• Trust dialog: "Workspace Trust Required" on first launch per directory; accept with Enter; persists.
• Resume: --continue verified headlessly to restore the prior chat.

Tests

• New test_cursor_threads_model_and_ignores_effort_axis in tests/fm-spawn-dispatch-profile.test.sh.
• New invalid-effort row (cursor:high) in tests/fm-bootstrap.test.sh.
• fm-spawn-dispatch-profile, fm-bootstrap, fm-composer-ghost, fm-grok-harness, fm-secondmate-harness, and fm-backend suites all pass on this branch.

🤖 Generated with Claude Code

[kunchenguid]

Thanks for the PR! This branch currently has a merge conflict with the base branch.

When you get a chance, please rebase onto (or merge) the latest base branch, resolve the conflict, and push. After that, checks will re-run and the PR will get looked at again.

_{Noted for firstmate#491 at 8d5af6f7.}

[cybercat-yanik]

Rebased onto latest main (b708731) and resolved the conflicts. Notes from the rebase:

• AGENTS.md: kept your new pointer to the harness-adapters skill instead of restoring the inline profile-axes list; the cursor axis row lives only in the skill's launch-profile table now.
• Extended the two adapter lists added on main since I branched: the secondmate-liveness trusted-harness case in bin/fm-bootstrap.sh, and kept the cursor test row alongside the new array-use/select validation rows in tests/fm-bootstrap.test.sh.
• Scoping note added to the skill: cursor is verified as a crewmate/secondmate adapter only. It has no tracked primary turn-end guard, PreToolUse seatbelt, or watcher wake adapter, so a cursor PRIMARY intentionally falls back to the unknown-harness supervision snippet (docs/supervision-protocols/unknown.md) rather than getting a named snippet.

fm-spawn-dispatch-profile, fm-bootstrap, fm-composer-ghost, fm-grok-harness, and fm-secondmate-harness suites all pass on the rebased branch.