feat(app): add Resume Session to continue previous conversations

[seibe]

Summary

Adds the ability to resume a previous Claude conversation by spawning a new Happy session with --resume <claudeSessionId>. This lets users continue where they left off without losing context.

Related issues

Addresses: #685 — support resuming Claude Code sessions when spawning from mobile.
Also relevant: #478, #621, #611, #353, #437 — various requests for session resume/continue functionality from mobile.

Comparison with similar PRs

• fix(cli): prevent session flags from leaking through on retry #644 — prevents session flags (--continue, --resume) from leaking through on retry in the local CLI launcher. This is a complementary fix for the local mode retry path; this PR implements the remote-mode resume feature via the daemon's spawn RPC, which is a separate code path. Both can coexist.
• feat: add pagination for loading older chat messages #308 (closed) pagination PR also touched sync.ts — no actual overlap with this feature.

How it works

• Reuses the existing spawn-happy-session / spawn-in-directory RPC — the daemon interprets the presence of a sessionId field as a resume request and appends --resume <id> to the CLI spawn command
• The daemon validates the session ID against a strict UUID regex before using it, guarding against injection in the tmux shell command path
• The UI only shows the resume option when the session is inactive, disconnected, and has the required metadata (claudeSessionId + machineId)
• The resume button is disabled with a "Machine is offline" subtitle when the target machine is not reachable

Changes by package

happy-app

• session/[id]/info.tsx: Add "Resume Session" action in Quick Actions group with online/offline machine status
• SessionsList.tsx: Add swipe-to-resume gesture (green "Resume" button alongside existing red "Delete")
• sync/ops.ts: New machineResumeSession() function that sends spawn-happy-session RPC with sessionId
• Translation files (10 locales): Add resumeSession, resumeSessionSubtitle, resumeSessionMachineOffline, failedToResumeSession keys

happy-cli

• daemon/run.ts: Handle sessionId in spawn payload — validate UUID format, append --resume <id> to tmux command or spawn args

Test plan

• Open session info for a completed session on an online machine → "Resume Session" button is green and pressable
• Tap Resume → new session is created and navigated to, Claude resumes the conversation
• Open session info for a session on an offline machine → button is grayed out with "Machine is offline"
• Swipe left on a resumable session in the list → green "Resume" button appears alongside "Delete"
• Session that is currently active → no resume button shown