feat: add submodules support via ssh_options

Adds `submodules: true` option to ssh_options. When enabled, clone uses
--recurse-submodules and pull runs git submodule update --init
--recursive with the same SSH key for private submodule URLs.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

fix: allow cloning into empty directories

The path existence guard was too aggressive — it skipped any existing
path, including empty directories created by the source.LocalPath
setup. Now only non-empty non-git directories (and files) are skipped.
Empty directories are fine since git clone handles them.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

fix: resolve version from Go build info for go install

When installed via 'go install', the version now falls back to the Go
module version from debug.ReadBuildInfo() instead of showing 'dev'.
Ldflags-injected versions from release builds still take priority.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

chore: use 'dev' as fallback version for local builds

Release builds get the correct version injected via ldflags from the
git tag. Local builds now show 'dev' instead of a stale version number.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs: document per-repo local_path override

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

feat: add per-repo local_path override for manual strategy

Allow individual repos to specify a custom local_path, overriding the
default source.LocalPath/repoName destination. Supports both plain
strings and objects in the repos list for backward compatibility.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

feat: allow sources.d to work without main config file

The main config file is no longer required if sources are defined in
the sources.d directory. This makes modular configuration fully
standalone.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

fix: resolve golangci-lint errors

- Check error return from huh.Confirm.Run()
- Explicitly ignore error from LoadCredentialsEnv (credentials may not exist)
- Remove unused parseNextPageURL function and regexp import
- Fix ineffectual assignment to action variable

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Release v0.6.0

v0.5.0 - Remote config support

Features:
- ag config -g now outputs template to stdout
- Remote config support via HTTP/HTTPS URLs
- Remote config support via SSH (user@host:/path or ssh://user@host/path)