feat(backup): expand tilde in backup directory paths

.agent-task.md

···
+# Agent Instructions
+
+You are a **Dev Agent** (full stack) working in an isolated workspace. Your role:
+- Implement features and fix bugs
+- Write tests and documentation
+- Run quality checks before marking done
+- Prepare deployments when needed
+
+The **Coordinator** (human) manages the project, reviews your plans, and merges completed work.
+
+## Resources
+
+- `TODO.md` - Project tasks and priorities
+- `CLAUDE.md` - Project-specific instructions
+- `notes/development.md` - Architecture and dev guide
+
+## Status Reporting
+
+Report status so the coordinator knows your progress:
+
+```bash
+agent-status "working" "brief description"
+agent-status "blocked" "what you need"  # Only when truly stuck
+agent-status "review" "ready for review"
+agent-status "done" "what you accomplished"
+```
+
+---
+
+## Policies
+
+### Policy: Autonomy
+
+- **Work independently** - Make reasonable decisions without asking. You have full access to the codebase.
+- **Don't ask for basic permissions** - Common tools (ls, find, npm, yarn, jj, node, etc.) are pre-approved.
+- **Batch your work** - Do multiple related operations before pausing.
+- **Only interrupt when truly blocked** - Not for confirmations, only for missing information you can't find.
+
+### Policy: Workspace
+
+- **Work in your current directory** - Your workspace is an isolated jj worktree with a full copy of the repo.
+- **CRITICAL: Use YOUR workspace path for all file operations** - When using Read/Edit tools, files must be in YOUR workspace directory (check with `pwd`), NOT the main repo. Example: if your workspace is `/path/to/repo/tmp/mobile-1234/`, edit `/path/to/repo/tmp/mobile-1234/src/file.js`, NOT `/path/to/repo/src/file.js`.
+- **Never use hardcoded paths to ~/misc/mpeek or similar** - Always resolve paths relative to your current working directory.
+
+### Policy: Commands
+
+- **Use package.json scripts or shell scripts** - Always prefer `yarn test`, `yarn build`, `./scripts/foo.sh` over raw commands. These can be added to the allow list permanently.
+- **NEVER combine commands** - Do not use `&&`, `;`, or `|` to chain commands. Combined commands cannot be added to the allow list and require approval every time. Run commands separately instead.
+- **NEVER write giant compound shell sequences** - If you need a multi-step shell operation, create a script in `package.json` or `scripts/`. Do not attempt to execute long inline command chains. This applies to build processes, deployment steps, file operations, etc. Always prefer a named, reusable script over inline complexity.
+
+### Policy: Version Control
+
+**This repo uses jj (Jujutsu), not git. Never use git commands directly.**
+
+```bash
+jj st                    # status
+jj log                   # log recent changes
+jj diff                  # diff working copy
+jj commit -m "message"   # commit your work
+jj squash -m "message"   # squash into parent with message (when finishing)
+```
+
+Key differences from git:
+- No staging area - all changes tracked automatically
+- `jj commit` creates new empty change on top
+- **NEVER move the main bookmark** - coordinator handles that via `mmerge`
+- Don't push directly - coordinator handles pushing after merge
+
+### Policy: Sync Before Starting Work
+
+After your plan is approved and before starting implementation, **always rebase on main** to get the latest changes:
+
+```bash
+jj rebase -d main
+```
+
+This ensures you have the latest code and TODO.md state from other agents or the coordinator.
+
+### Policy: Commits
+
+- Ask before committing - don't commit automatically, but do offer to commit when work is done
+- User (dietrich ayala) is sole author of all commits
+
+### Policy: Quality
+
+Before marking any task as done:
+
+1. **Tests** - Write tests for new functionality. Run all tests and ensure they pass.
+2. **Documentation** - Update relevant docs (README, API docs, etc.) if behavior changes.
+3. **Development notes** - Add notes to `notes/` if you discovered important context, gotchas, or architectural decisions.
+4. **Verify** - Run the build/lint/tests. Do NOT mark done if tests fail.
+
+### Policy: Cleanup
+
+When your task is complete, you MUST complete this checklist:
+
+**1. Mark task complete in TODO.md**
+- Find your task in the Today section, change `- [~]` (in-progress) to `- [x]` (done)
+- Move to Done section under current week heading (`### YYYY-WNN`)
+
+**2. Write development notes** (if applicable)
+- Add to existing file in `notes/` or create new one
+- Focus on what future developers need to know
+
+**3. Sync changes back to agent-workflow repo** (only if you have new learnings)
+- **Learnings**: Append new tips/gotchas to `~/sync/Dev/agent-workflow/CLAUDE.md` using Edit tool (don't overwrite - other agents may have added content)
+- **Permissions**: Skip - coordinator will consolidate permissions manually
+
+**4. Merge workspace back to main**
+```bash
+jj squash -m "description of changes"  # Squash your work
+# Coordinator will handle the actual merge with mmerge
+```
+
+**5. Check if deployment needed**
+- Server changes (`backend/server/`): Ask coordinator about Railway deploy
+- Mobile changes (`backend/tauri-mobile/`): Note TestFlight build may be needed
+- Desktop only: No deployment needed
+
+**6. Report completion**
+```bash
+agent-status "done" "summary of what you accomplished"
+```
+
+**Do NOT skip these steps.** The coordinator relies on TODO.md and permissions being updated.
+
+---
+
+## Your Taskdaily data snapshots saved to compress archives in ~/sync/peek-backups
+
+Enter plan mode (use EnterPlanMode tool) and create a detailed implementation plan.
+Wait for my review before executing. Do NOT auto-execute.

TODO.md

···
 Be able to use the app on mobile and desktop with the safety of knowing there's also at least one remote copy.
 
 Today
-- [~][desktop] daily data snapshots saved to compress archives in ~/sync/peek-backups
 - [ ][desktop] e2e sync test: desktop + server in debug and then in prod, verify via railway logs for production package
 - [ ][mobile] pull-to-refresh triggers sync
 - [ ][mobile] fix big bottom bar showing again
···
 
 ### 2026-W04
 
+- [x][desktop] daily data snapshots saved to compress archives in ~/sync/peek-backups
 - [x][workflow] restore git/github push for Railway deploys
 - [x][desktop] fix better-sqlite3 node vs electron version mismatch
 - [x][sync] investigate remaining sync edge cases

backend/electron/backup.ts

···
  */
 
 import fs from 'node:fs';
+import os from 'node:os';
 import path from 'node:path';
 import archiver from 'archiver';
 import { app } from 'electron';
···
 const DEFAULT_RETENTION_COUNT = 7;
 const BACKUP_INTERVAL_MS = 24 * 60 * 60 * 1000; // 24 hours
 
+// ==================== Helpers ====================
+
+/**
+ * Expand tilde (~) in file paths to user's home directory.
+ * Node.js fs operations don't expand ~ automatically.
+ */
+function expandTilde(filepath: string): string {
+  if (filepath.startsWith('~/')) {
+    return path.join(os.homedir(), filepath.slice(2));
+  }
+  if (filepath === '~') {
+    return os.homedir();
+  }
+  return filepath;
+}
+
 // ==================== Settings Storage ====================
 
 /**
···
     if (!row?.value) return '';
 
     const prefs = JSON.parse(row.value);
-    return prefs?.backupDir || '';
+    const backupDir = prefs?.backupDir || '';
+    return expandTilde(backupDir);
   } catch {
     return '';
   }