Captain session identity: session_id wiring (#709) + self-describing -n names (#708)

[tu11aa]

Summary

Two related identity gaps closed together (same files, one branch):

#709 — captain-bound channel now carries session_id. captain-channel-factory.ts hardcoded sessionIdFor: () => undefined. Resolves it from the same registry entry statusFor already reads (keyed by the launch-time socket path via readClaudeStatusBySocketPath), extracted into a small testable captainSessionIdFor. This:

• restores the pid-reuse guard at registry.ts:137 (was silently skipped for every captain send)
• removes the "Another Claude session sent a message:" wrapper + peer-guardrail paragraph on captain-bound CREW DONE/ping/Telegram sends
• falls back to omitting session_id (never throws) when the captain hasn't registered in ~/.claude/sessions/ yet

#708 — captains and crews now get a self-describing name. squadrant never passed claude's -n, --name flag, so display names auto-derived from the cwd basename (squadrant-fix-706-67, helpa-06) — a crew calling ListAgents couldn't tell its own captain apart from an unrelated session and misrouted its report. Added captainSessionName(project) / crewSessionName(project, name) in @squadrant/shared (sanitized to the same safe-filename charset captainSocketPath() already enforces) and wired into both claude launch paths:

• buildAgentCmd (captain/command, launch.ts) → squadrant-captain-<project>
• claude driver's buildCommand (crew, crew-spawn.ts) → squadrant-crew-<project>-<name>

-n is claude-only. Added as an optional SpawnOptions.sessionName field that only the claude driver reads — codex/gemini/opencode buildCommand implementations were checked and ignore unknown fields safely (each reads only the specific opts.* keys it cares about), so this is a no-op for them.

Proof (#709 success criterion)

packages/cli/src/lib/__tests__/captain-channel-factory.test.ts builds a real ClaudePeerChannel wired the same way buildCaptainChannel() is, with a stub wire capturing the envelope:

• captain resolvable in registry → envelope.session_id === "sess-captain-1"
• captain not resolvable → envelope.session_id === undefined, send() still resolves (no throw)

✓ captainSessionIdFor > resolves the sessionId from the registry entry matching the captain's socket path
✓ captainSessionIdFor > returns undefined, not throw, when the captain has not registered yet
✓ captain envelope carries session_id end-to-end (#709) > includes session_id when the captain is resolvable in the registry
✓ captain envelope carries session_id end-to-end (#709) > omits session_id (does not throw) when the captain is not resolvable in the registry

Test plan

• pnpm build clean
• pnpm test: 2734 → 2747 tests (207 → 208 files), all passing — 13 new tests, none deleted
• node dist/index.js --help exit 0
• node dist/squadrantd.js --help exit 0
• New/updated tests: registry.test.ts (readClaudeStatusBySocketPath sessionId), captain-channel-factory.test.ts (new, envelope proof), session-name.test.ts (new), launch.test.ts (resolveCaptainSessionName), launch-captain-socket.test.ts (per-project name regression, same class of bug as [agent-report] launch.ts builds the captain messaging socket from the positional arg — every --all / parallel launch collides on squadrant-captain-undefined.sock #706), crew-spawn.test.ts (sessionName wiring)

Not touched: daemon, captainChannel/controlChannel semantics, no drive-by refactors.