chore: change default data/config dir from ~/Library/Application Support to ~/.ao

[harshitsinghbhandari]

Problem

The daemon currently stores all durable state (SQLite DB, WAL, worktrees, run file) under the platform-default os.UserConfigDir() path, which on macOS expands to:

~/Library/Application Support/agent-orchestrator/

This is buried, hard to find for debugging, and inconsistent with the CLI-tool convention of keeping state in a visible dotdir.

Proposed change

Move the default root to ~/.ao/, so the layout becomes:

Path	Purpose
~/.ao/data/	SQLite DB + WAL (AO_DATA_DIR default)
~/.ao/running.json	Daemon PID/port handshake (AO_RUN_FILE default)
~/.ao/worktrees/<project>/<session>/	Per-session git worktrees

AO_DATA_DIR and AO_RUN_FILE env overrides remain unchanged — only the fallback changes.

Affected code

• backend/internal/config/config.go — resolveDataDir() (line ~202) and resolveRunFilePath() (line ~192): replace os.UserConfigDir() + "agent-orchestrator/..." with os.UserHomeDir() + ".ao/...".

Notes

• Existing installs will lose their data on upgrade unless they set AO_DATA_DIR explicitly or migrate manually — worth a note in the release.
• Cross-platform: ~/.ao/ works fine on macOS, Linux, and Windows (WSL). Native Windows (AppData) is a separate discussion.