feat(orchestrator): bash port of pa-start / sa-start launchers

[evannadeau]

Summary

Adds pa-start.sh and sa-start.sh alongside the existing .ps1 / .bat launchers in plugins/orchestrator/skills/install-launchers/scripts/. Users running Claude Code from a POSIX shell (WSL, Linux, macOS) can now spawn PA/SA sessions without PowerShell interop.

Motivation: running pa-start.bat from WSL requires powershell.exe interop, which loses the Linux-native env (PATH, shell aliases, etc.) and adds a Windows-side handoff that's unnecessary when claude itself runs perfectly in WSL bash. This PR closes that gap.

Behavior parity with the .ps1 sources (0.30.28)

• Resume by display name: greps ~/.claude/projects/<hash>/*.jsonl for Session renamed to: <name> lines, picks newest match, resolves to UUID. Project-hash transform matches CC's own scheme (POSIX paths reduce to s|/|-|g plus leading-dash trim — no \ or : to handle).
• pa-start.sh singleton check: reads .orchestrator-state/agent-channel/sessions.json via jq, finds role=prime entries with heartbeat <90s, demotes them to subordinate, 2s Ctrl+C grace, then proceeds. jq's fromdateiso8601 rejects fractional seconds, so the heartbeat string is preprocessed with sub("\\.[0-9]+Z$"; "Z") before parsing.
• Env wiring: MCP_TIMEOUT=30000, ORCHESTRATOR_PROJECT_ROOT, ORCHESTRATOR_AGENT_ROLE (+ SPAWNBOX_ alias), ORCHESTRATOR_PA_PERMISSION_RELAY=1, ORCHESTRATOR_AGENT_NAME (when explicit) — same set as .ps1.
• PA hardcodes --effort max (per 0.30.28 policy); SA exposes optional --effort with low|medium|high|xhigh|max validation.
• Marketplace slug uses the same __ORCH_MARKETPLACE__ placeholder the .ps1 sources use; install-launchers SKILL.md sed-substitutes it at copy-into-project time.

Differences from .ps1 (out of scope or N/A for bash)

• No wt.exe tab spawn / gold-tab color. POSIX shells don't have an equivalent terminal-window manager invocation. exec claude runs in the current shell. Users wanting a separate window run the launcher inside their preferred terminal-emulator tab.
• No discord-start.sh (yet). The Discord plugin install + the dual --channels / --dangerously-load-development-channels attach is tightly coupled to the Windows-side Discord setup. WSL/Linux users who need Discord-ops can run discord-start.bat via interop or contribute a .sh port in a follow-up.

SKILL.md updates

Install workflow now copies 8 files instead of 6, install -m 0755s the .sh variants, and documents the per-platform variant guide + runtime deps (jq + GNU coreutils for pa-start.sh's singleton check; sa-start.sh has no deps beyond bash 4+). Usage examples block now lists both Windows and POSIX invocations.

Test plan

Tested on Ubuntu-24.04 WSL with bash 5.2.21, jq 1.7.1, GNU coreutils, against a live orchestrator MCP at 0.30.28.

Verified end-to-end — ./sa-start.sh invoked from a fresh WSL terminal spawned a real claude process which booted the orchestrator MCP and registered in sessions.json:

PID 2023  claude --dangerously-load-development-channels plugin:orchestrator@spawnbox-dev-claude-plugins --name SA-2026-05-11-19-50-34
PID 2172  npm exec bun run plugins/orchestrator/dist/server.js

{
  "session_id": "d3614a60-146d-4e8a-bcd8-535d99e11ea7",
  "id8": "d3614a60",
  "role": "subordinate",
  "name": "SA-2026-05-11-19-50-34",
  "started_at": "2026-05-12T02:50:42.090Z",
  "last_heartbeat_at": "2026-05-12T02:51:12.146Z"
}

Confirms the whole chain: arg passing, env propagation to MCP, role/name registration, agent-channel heartbeat, id8 derivation.

Additional unit-level checks:

• bash -n syntax check clean on both scripts
• --help renders header docs
• sa-start.sh fresh → auto-name SA-YYYY-MM-DD-HH-MM-SS, all 7 env vars set, args in correct order (verified via PATH-shimmed claude that prints what would be exec'd)
• sa-start.sh --name SA-foo --effort max → name override + --effort max appended after --name
• sa-start.sh --effort bogus → validation rejects, exit 2
• pa-start.sh fresh (no prime running) → --effort max hardcoded in args, role=prime env, singleton check correctly no-ops
• jq singleton-check query dry-run against a live sessions.json correctly returns [] when no prime is active and parses fractional-second ISO-8601 timestamps without error

Not exercised in this PR (low risk, deferred):

• Singleton-demote path against an actual fresh role=prime heartbeat. The jq query is verified; the mv "$tmp" "$state_file" write path is straightforward. First real PA invocation against a stale-PA state will exercise it.
• Resume-by-name path against a real Session renamed to: JSONL entry. The grep + ls -t logic is straightforward; first real use will exercise it.

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